This has occurred a number of times albeit not consecutively.
The program will crash when I copy a table. The normal crash dialog comes up where I can quit or restart heidi. I recover without issue and data is not lost. The table copy does complete. I'm running the latest 188.8.131.5250 (64 bit) Windows 10 version as of 2021-03-21.
Let me know if I can send you something to help trace this.
I'd also like to add a feature request to remember column widths per table or query when they are resized. It would be very helpful when switching among tables and when relaunching the program.
By the way I just tried the dark themes and they look great.