I started looking at the file in order to figure out what causes T56916.
Turns out that this file is huge and has extremely long functions (>1000 lines).
This addon makes heavy use of bpy.ops..., that makes it hard to assume anything about what is happening...

I could not fix the bug yet, but found a lot of statements that make no sense, so I decided to clean them up a little (fortunately regex worked well here).