Hi there. Sorry you're having a problem with this but I of course do not expect a crash to occur when your map is being re-imported.
The best course of action for such issues is to open an issue on my GitHub page: https://github.com/Seanba/SuperTiled2Unity/issues
The first thing I'd like to look at is your Editor log. This link will help you find that on your OS: https://docs.unity3d.com/Manual/LogFiles.html
I'd probably also want to look at your project to see if I can replicate the problem. If that isn't possible (which is understandable) then a small project that does have the bug would be useful.
I'm not sure how helpful having a Discord server would be but I'm open to trying it out. Here's an invite: https://discord.gg/48KsnG