Is there some location where older versions of the ExifToolGUI can be found and downloaded?
Looks like the bug is 5.14 may be a real issue for a while.
I have just posted links to the final versions of each major release here (https://exiftool.org/forum/index.php/topic,2750.msg22260.html#msg22260).
As well as these, version 5.13 is also available on the server although I didn't make a link to it.
- Phil