I recently switched my FE to RetroFE due to it's support for HD resolutions. After some tinkering to get it working, everything seemed fine. Except when I tried to run more demanding, high framerate MAME games (CAVE shooters in particular), my FPS would drop into the single digits, making the games totally unplayable. Most other games worked fine - it was specifically the shooters with the issue. And this was ONLY if the games were launched through RocketLauncher on a CLI call from RetroFE. If I ran from MAME directly, or from RocketLauncher UI, everything ran fine.

After checking the bezel settings, resolution, and plugin settings, everything checked out. Since the problem seemed to be RetroFE's fault, I decided to check the "launch as admin" settings, which I had already set at install. BUT...for some reason I had turned the program's compatibility settings to "Windows 8". I'm running everything on Windows 10. As soon as I turned off compatibility for RetroFE (still running it as Admin), everything magically ran full speed. Not sure why the compatibility setting for the front end had anything to do with the emulator speed, but it did.

Just thought I would post this solution, as the cause really didn't make any sense.