Cosmetic filters not saving

[jaaaco-j]

Prerequisites

• I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• This is NOT a YouTube, Facebook or Twitch report. These sites MUST be reported by clicking their respective links.
• This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• The issue is not present after disabling uBO in the browser.
• I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• uBO is the only extension.
• uBO uses default lists and settings.
• using a new, unmodified browser profile.

Description

whenever i try using the element picker to create a cosmetic filter, it hides the element until the browser is restarted. When trying to do it directly on ublock's my filters page it just disappears on refresh even though i hit save changes button.

A specific URL where the issue occurs.

reddit.com

Steps to Reproduce

go to a website
click the element picker
apply a cosmetic filter
close the browser
go back to the website

Expected behavior

Filtered element staying hidden and my filter list having an entry

Actual behavior

Filtered element appears again and the my filter list is empty

uBO version

1.61.2

Browser name and version

Vivaldi 7.0.3495.27 (Stable channel) (64-bit)

Operating System and version

Windows 10, ver. 22H2, build 19045.5247

[gwarser]

Please share Troubleshooting Information from uBO Dashboard -> Support tab.

[krystian3w]

I can reproduce occasionally with Firefox 115.19 - 133.0.3 (Unfortunately, it is so, rare that I can't afford to keep the site, browser & add-on consoles opened in the background) with uBo 1.5.5+ (I don't use GNU/Linux on a daily basis, so if you were able to reproduce the problem with Chromium then maybe it is specific to Windows 7, 10 and 11 only with rare chance reproduction on Android for Phones), the close browser step may is not needed (at my side saving may fail almost click "create/apply"), then possible use refresh in STR:

• go to a website
• click the element picker
• apply a cosmetic filter
• refresh tab

firefox-storage-test.glitch.me - all "Totally Working".