diff --git a/pyflask/manageNeuroconv/manage_neuroconv.py b/pyflask/manageNeuroconv/manage_neuroconv.py
index e6d2fabc9..27727640b 100644
--- a/pyflask/manageNeuroconv/manage_neuroconv.py
+++ b/pyflask/manageNeuroconv/manage_neuroconv.py
@@ -258,7 +258,11 @@ def get_metadata_schema(source_data: Dict[str, dict], interfaces: dict) -> Dict[
     """Function used to fetch the metadata schema from a CustomNWBConverter instantiated from the source_data."""
     from neuroconv.utils import NWBMetaDataEncoder
 
-    converter = instantiate_custom_converter(source_data, interfaces)
+    resolved_source_data = replace_none_with_nan(
+        source_data, resolve_references(get_custom_converter(interfaces).get_source_schema())
+    )
+
+    converter = instantiate_custom_converter(resolved_source_data, interfaces)
     schema = converter.get_metadata_schema()
     metadata = converter.get_metadata()
 
@@ -423,7 +427,11 @@ def convert_to_nwb(info: dict) -> str:
 
     resolved_output_path.parent.mkdir(exist_ok=True, parents=True)  # Ensure all parent directories exist
 
-    converter = instantiate_custom_converter(info["source_data"], info["interfaces"])
+    resolved_source_data = replace_none_with_nan(
+        info["source_data"], resolve_references(get_custom_converter(info["interfaces"]).get_source_schema())
+    )
+
+    converter = instantiate_custom_converter(resolved_source_data, info["interfaces"])
 
     def update_conversion_progress(**kwargs):
         announcer.announce(dict(**kwargs, nwbfile_path=nwbfile_path), "conversion_progress")
diff --git a/src/renderer/src/stories/JSONSchemaForm.js b/src/renderer/src/stories/JSONSchemaForm.js
index 36060fd91..c7e4d865f 100644
--- a/src/renderer/src/stories/JSONSchemaForm.js
+++ b/src/renderer/src/stories/JSONSchemaForm.js
@@ -23,7 +23,7 @@ const encode = (str) => {
 
 const additionalPropPattern = "additional";
 
-const provideNaNMessage = `<br/><small>Type <b>NaN</b> to represent an unknown value.</small>`;
+const templateNaNMessage = `<br/><small>Type <b>NaN</b> to represent an unknown value.</small>`;
 
 import { Validator } from "jsonschema";
 import { successHue, warningHue, errorHue } from "./globals";
@@ -378,8 +378,8 @@ export class JSONSchemaForm extends LitElement {
         throw new Error(message);
     };
 
-    validateSchema = async (resolved, schema, name) => {
-        return await validator
+    validateSchema = (resolved, schema, name) => {
+        return validator
             .validate(resolved, schema)
             .errors.map((e) => {
                 const propName = e.path.slice(-1)[0] ?? name ?? e.property;
@@ -399,8 +399,8 @@ export class JSONSchemaForm extends LitElement {
 
                 // Allow referring to floats as null (i.e. JSON NaN representation)
                 if (e.message === "is not of a type(s) number") {
-                    if (resolvedValue === "NaN") return;
-                    else e.message = `${e.message}. ${provideNaNMessage}`;
+                    if ((resolvedValue === "NaN") | (resolvedValue === null)) return;
+                    else if (isRow) e.message = `${e.message}. ${templateNaNMessage}`;
                 }
 
                 const prevHeader = name ? header(name) : "Row";
@@ -422,7 +422,7 @@ export class JSONSchemaForm extends LitElement {
         const copy = structuredClone(resolved);
         delete copy.__disabled;
 
-        const result = await this.validateSchema(copy, this.schema);
+        const result = this.validateSchema(copy, this.schema);
 
         const resolvedErrors = this.#resolveErrors(result, this.base, resolved);
 
@@ -815,7 +815,7 @@ export class JSONSchemaForm extends LitElement {
         const skipValidation = !this.validateEmptyValues && value === undefined;
         const validateArgs = input.pattern || skipValidation ? [] : [value, schema];
 
-        const jsonSchemaErrors = validateArgs.length === 2 ? await this.validateSchema(...validateArgs, name) : [];
+        const jsonSchemaErrors = validateArgs.length === 2 ? this.validateSchema(...validateArgs, name) : [];
 
         const valid = skipValidation ? true : await this.validateOnChange(name, parent, pathToValidate, value);
 
@@ -860,9 +860,16 @@ export class JSONSchemaForm extends LitElement {
                 // Throw at least a basic warning if a non-linked property is required and missing
                 if (!hasLinks && isRequired) {
                     if (this.validateEmptyValues) {
+                        const rowName = pathToValidate.slice(-1)[0];
+                        const isRow = typeof rowName === "number";
+
                         errors.push({
                             message: `${schema.title ?? header(name)} ${this.#isARequiredPropertyString}. ${
-                                schema.type === "number" ? provideNaNMessage : ""
+                                schema.type === "number"
+                                    ? isRow
+                                        ? templateNaNMessage
+                                        : "<br><small>Use the 'I Don't Know' checkbox if unsure.</small>"
+                                    : ""
                             }`,
                             type: "error",
                             missing: true,
diff --git a/src/renderer/src/stories/JSONSchemaInput.js b/src/renderer/src/stories/JSONSchemaInput.js
index 3c61f412b..aae940a4b 100644
--- a/src/renderer/src/stories/JSONSchemaInput.js
+++ b/src/renderer/src/stories/JSONSchemaInput.js
@@ -435,7 +435,7 @@ export class JSONSchemaInput extends LitElement {
                 white-space: nowrap;
             }
 
-            .nan-handler label {
+            .nan-handler span {
                 margin-left: 5px;
                 font-size: 12px;
             }
@@ -1074,12 +1074,14 @@ export class JSONSchemaInput extends LitElement {
 
                             // const isBlank = value === '';
 
-                            if (isInteger) newValue = parseInt(value);
-                            else if (isNumber) newValue = parseFloat(value);
+                            if (isInteger) value = newValue = parseInt(value);
+                            else if (isNumber) value = newValue = parseFloat(value);
 
                             if (isNumber) {
                                 if ("min" in schema && newValue < schema.min) newValue = schema.min;
                                 else if ("max" in schema && newValue > schema.max) newValue = schema.max;
+
+                                if (isNaN(newValue)) newValue = undefined;
                             }
 
                             if (schema.transform) newValue = schema.transform(newValue, this.value, schema);
@@ -1090,7 +1092,7 @@ export class JSONSchemaInput extends LitElement {
                             //     if (!regex.test(isNaN(newValue) ? value : newValue)) newValue = this.value // revert to last value
                             // }
 
-                            if (!isNaN(newValue) && newValue !== value) {
+                            if (isNumber && newValue !== value) {
                                 ev.target.value = newValue;
                                 value = newValue;
                             }
@@ -1108,19 +1110,20 @@ export class JSONSchemaInput extends LitElement {
                     ${isRequiredNumber
                         ? html`<div class="nan-handler"><input
                         type="checkbox"
-                        ?checked=${this.value && Number.isNaN(this.value)}
+                        ?checked=${this.value === null}
                         @change=${(ev) => {
                             const siblingInput = ev.target.parentNode.previousElementSibling;
                             if (ev.target.checked) {
-                                this.#updateData(fullPath, NaN);
+                                this.#updateData(fullPath, null);
                                 siblingInput.setAttribute("disabled", true);
                             } else {
                                 siblingInput.removeAttribute("disabled");
                                 const ev = new Event("input");
                                 siblingInput.dispatchEvent(ev);
                             }
+                            this.#triggerValidation(name, path);
                         }}
-                    ></input><label>I Don't Know</label></div>`
+                    ></input><span>I Don't Know</span></div>`
                         : ""}
                 `;
             }