You presumably downloaded ExifTool from www.exiftool.org, which isn't our website and has no connection to us. Unless you assume we made every piece of software on earth, it should be obvious we didn't make ExifTool.
The script which talks to ExifTool came from our forum, but was posted by a user. We may be able to help with user-made scripts but we aren't experts when it comes to most of them.
I don't know if the issue is in ExifTool, or the script, or something else (e.g. some other script or metadata DLL might be taking a long time to process an earlier file, which could cause a backlog in the background threads that request and generate metadata). If the problem happens again, those are things that can be debugged by testing if the script is actually being run and, if it is, what the inputs and outputs are when it calls ExifTool in turn.