I understand your hesitation regarding a different version as things have changed over time with iTunes. I explained my situation in this post some time ago:
I applied the codesign command to an iTunes copy from a backup and it worked for that but not for the Retroactive installed one as it works differently from what I’ve read. So if you have a backup of the one that worked, the codesign command I mentioned in that post should work. I know you want 12.9.5 but if you have a working copy, you should be able to use it similar to what I did for version 10.7 which is the one I like.