Might need to post some crash logs or similar to have any diagnosis. Might not be anything special, but at least it will say something about why it’s crashing.
How did you go about updating Retroarch?
Latest Retroarch, I’m guessing is 1.9.0? What arguments were used when making?
Latest OS, do you mean clockwork OS 0.5, or Debian OS Buster? Or possibly just the launcher updated?
So Cores start, but loading content doesn’t work? How are you determining if your cores have started? Are you running Retroarch, and then loading the cores; and then loading content? Or are you using the action.config files from the launcher?
Sounds like you have an idea of what you’re doing, but if you would rather not have to mess around with troubleshooting, potentially try my custom image out. It has most things updated to the newest version, and tested to be working.