@stonev it should not be named "temp.rmp", or at least I've never had a remap file get created with that file name. it should be following the expected file name nomenclature which is in line with the other file name you mentioned "sega genesis.rmp" and the other should be "sega master system.rmp"
not sure what to think about that goofy temp file name business, it is suspect to some other potential unknown issue though.
any chance you installed/unpacked more than one instance of retroarch? and when you're testing from "within" the frontend and "outside" the frontend, are you sure you are running the exact same instance of retroarch? this would be the easiest explanation since making a setting change in one of the instances wouldn't impact the other and vise versa. but it doesn't really jive with the first bit about the temp file name, because that in itself is not normal per my experience. then again, I don't let the frontend manage my emulators or store them within the frontends directory structure so it could be related to that. i'm also not on the latest beta i'm on 13.19 and RA 1.16