I've never seen or heard of this issue. By any chance, could you send me a file that it crashes on? That or a video showing the crash. You can send them here: https://www.moderncsv.com/report-a-bug/
In the meantime, I popped open Process Explorer. Here's a slightly abbreviated stack of the only running thread -- the rest are in waiting states. I don't know much about Qt, so this doesn't really mean anything to me. But it looks like it's maybe some sort of locking issue.
1. Open Modern CSV.
2. Open any file.
3. Select any cell.
4. Hit ctrl-c.
Expected: The cell contents would be copied.
Actual: The program becomes completely unresponsive with high CPU usage and must be force-quit.
Happy to help however I can, because so far I really like this product and I want to be using it.