Unexpected signal processing between state

[Ranc20]

Hi, i'm trying to debug some unexpected behaviour in the running workflow.

Workflow simplified flow :
Workflow A has state B and C. State B wait for signal D and State C wait for signal E.
If state B received a signal it will process some data and move to state C.
if state C received a signal it will process some data and move to state B.
the flow will go back and forth between these two state before the workflow finish.

there is an unexpected case where state B is signaled more than one signal D. The state move properly to next state (state C), but after state C completed the task and move to state B again, state B will directly processed the data without waiting the signal first like it should.

why this behaviour happen ?

Thanks.