Mame 2015 on Series S - some games won't load

I have a really odd issue, maybe someone here can help me out…

I have been running Mame on an Xbox Series S for a while now, not 100% sure of versions, but the first one I downloaded back end of August 2021 (RetroArch-msvc2017-UWP_x64) and the updated it in early September (RetroArch-msvc2019-UWP_x64). I used this version up to about a week ago when I updated to 1.10.0, and today I have updated to 1.10.1.

I have been trying out various roms on Mame, sorted by company and I stress that the majority of these work. I have been very careful to download the correct romset for the particular version of Mame I am running, and have found Mame 2015 to be prettu good in terms of games supported that run with no issues.

Having said that, I have encountered an issue I have no idea how to resolve.

I am simply trying to run either Ridge Racer, Ridger Racer 2 or Rage Racer on Mame 2015 (these are all Namco System 22). For some reason when I try and launch these by loading the content, then selecting the Mame 2015 core, Retroarch crashes back to the dev mode dashboard.

I found an odd workaround in the version of Retroarch I was running from early September 2021, in that if I loaded a working game, I could click the left trigger on the pad and it brought up an in Mame ‘Select new game’ menu, this allowed me to load a previosuly selected rom, even if it crashed Retroarch while attempting to load the content through the UI. This way I was able to run all these versions of Ridge/Rage Racer. I have no idea why this made a difference, but it did.

With the release of 1.10.0, the in Mame ‘Select new game’ menu only shows the game you are currently in, there is no way for me to chose a different game, so this backdoor method of loading Ridge Racer is gone.

My question is simple - why do some games, even with the correct romset, not load in Mame from the UI, crashing it back to the dashboard? And why did I have that workaround that no longer exists, but did load the game?

Does anyone have Ridge Racer working on an Xbox Series S/X port of Mame?

Secondly, how do I get CHD files working in the Xbox version of Mame? Is it possible?

Any help on the above would be hugely appreciated.

Thanks, Pul