All the specialized NPC or other stuff directly related to 5E is guarded in both the .xml and .lua code to only come into effect for the 5E ruleset - so if there are bugs in one of the superficially tested rulesets I listed - for sure mention it. Should all be the exact same code except where things are unavailable for non 5E rulesets.
The only reason I did not do 2E (all rulesets available to me as part of ultimate download) is because they had already gone a different path for implementing NPC inventories and I did not want to spend time figuring out any duplicate sets of coding to fully support just that one ruleset. For sure I went a different path where I did not have to duplicate branches of code.
In any case, I'm fine with bugs. If I don't think they are a bug or a natural limitation in my ability to test on my setup in a given ruleset, I'm not shy about stating it :) Nor am I worried about looking bad if I do that. I'd much prefer someone telling me something than not - and if they can actually give me a duplicatable scenario in my setup (raw FGU ultimate license without any extensions or with the extensions in my signature) I will absolutely look into it.

