WFL editor crashes if I click on some tasks

SUMMARY

The new WFL editor crashes if I click on some specific tasks. The affected actions are all part of self developed packs. It affects multiple actions belonging to multiple packs.
The same action is used two times in the workflow, one task can be edited the other one crashes the editor. -> I don't think it is related to my pack and action. But till now I have not identified what exactly makes the difference for the tasks working and the ones not working.

STACKSTORM VERSION

st2 3.4.0, on Python 3.6.8

OS, environment, install method

redhat:enterprise_linux:7.9

Steps to reproduce the problem

I can not share my current workflow and self developed packs, but I will check later if I can create an example workflow. Therefore I need to know what exactly the issue is, maybe someone can already give me a hint by looking at the error I get from Firefox or can tell me what I should check in advance. Otherwise I need more time to identify it on my own.

Expected Results

Move and edit tasks like others.

Actual Results

The editor crashes. (white page) used Browser: Firefox 86.0

Debug Output:

No source file, test, or entry point is identified in the report. Start by reproducing the crash with a minimal workflow in the WFL editor and inspect the Firefox 86.0 debug output; compare tasks using the same action. Done means affected tasks can be moved and edited without the editor showing a white page.