I've looked at the renaming issue...actually there is no issue
In case the rename operation is not supported, the file is handled as "not renamed" and moved to backup (but packed there as zip...so better check your backupfolder for zips). This is done with the scanner advanced option "move not renamed sets/roms to backup". If this option is not ticked, nothing happens and the files stay in the archive and are listed as failed renames.
I have no problems with renaming a 7.20 compressed 7z with 7.29a.
7Zip 9.29a uses lzma2 as default compression method...most likely t7z can't handle this correctly...but actually I don't care.
What I might think of is a general quick test at startup if the rename operation is available or not.
But again, there is no file loss, the move to backup is intended by the mentioned option, however it uses zip for the backups.