Very interesting. You may be on to something. I believe that this is the first time I've tried to import anything since upgrading to Montery a month ago.
When i go to System Preferences->Security and Privacy->Privacy->Files and Folders and then unlock the little padlock, the + under the list is greyed out and does not function. The minus is not greyed out. Media Center is on the list with a subitem Removable Volumes with the box checked. All my music files are on an SSD drive hooked to my iMac via USB-C to the back of the iMac. I can play music without problem (from the external SSD), but is it possible that Media Center might need access to other folders? In addition, I've been playing around and i get the same crash when trying to import any folder I've had in my library for years and that also causes a crash. Before now, it would just go through the update process but not change anything since the folder was already in my library. I think this eliminates it being the actual files themselves, but rather the process of accessing the files for import.
I'm stuck at this point, but i'd appreciate any suggestions. I did just try to backup the media library fron the File->Library->Backup Library in Media Center. The backup goes to my Documents folder which is in the cloud and it worked without problem.