Sometimes you have to get a little lucky

That was a quick turnaround, wasn't it?

By sheer luck I found the cause of the problems I lamented in my last devlog. 
Turns out it is indeed a bug in the godot engine as its threading implementation does not handle refcounted objects correctly.
Knowing that, this is an easy fix - just a single line of code to switch one class to a non-refcounted type and the crashes on exit are gone.
Multi-threading performance features are now restored on all platforms.

Equipped with this knowledge I can now set out to once more rework my implementation to hopefully eliminate all felt load times at startup.