Scenario editor bugs out

[CR4CE]

Hi!

I'm trying to edit myself a custom starting scenario, but I am running into an issue with the editor. When selecting any "drop-down" menu, like adding a part or selecting which faction I spawn as, I can hear the UI-sound but nothing shows up. After backing out my debug log is filled with one error.

I have pasted the error message here:
https://pastebin.com/dGDA6HsV

The error pops up continuously or so many times that the debug log stops logging it:
https://pastebin.com/hNVZcGT7

My modlist:
https://pastebin.com/wJDMamcc

I am using the latest public build via Steam: 1.3.3389 (64-bit) and have made a local copy of all the mods, since I am expecting there to be issues with the release of 1.4. and might want to continue playing the run (if it doesn't crash and burn, figuratively and literally )

Has this a fix or do I have to root out the culprit in my mods?