This is annoying for me and others because when moving a plate, the error occurs and force exits me without the project being saved.
These are usually un-recoverable errors (ie, GPlates cannot continue to run due to an inconsistent internal state - usually means a bug), so being able to save your project is not possible.
Can you send me the error message (preferably the GPlates_log.txt file, which contains the source code line of the error)?