I am not sure what Unity version reported these issues. Last version I have tested with was 2018. I realize that there are missing features that prevents me from going with final release soon -- mainly, isometric maps are not yet supported.
Maybe a version 0.10 at some point? I don't use isometric maps right now so it's not interesting for me. I'm using Unity 2019.3.15f (latest personal version available). I have logs for the warning messages and also logs for sometimes when it throws an error and refuses to import until unity restarts. Do you have the code in a respiratory like github where I can make comments and offer a commit? Also, I'm interested in giving something if money helps.