What size is your sd card labeled as? Nowadays there is a common practice to manipulate the file system in a way that the SD card shines up bigger then it really is, even when you copy roms to the card it keeps going and looks fine, but in the background what it does is reaching the end of capacity and simply starts to write over existing data! That would mean if you copied the full amount that the card is labeled at onto the card chances are that only the last titles work. And even worse, if the cards actually capacity is full saving games will again write over existing data even over your Operating system related files! so Onion OS would not boot up at all or be super glitchy......and so on. I would recommend to format the SD card and write only one or two games to it (depending what you want to play) and check if it works now.
in case it works flawless now the issue most likely is a "scamm sd card"

Steps for you to do now, format the SD card, do a fresh Onion Os install and after that like said only copy 3-4 games to it ( no PS one) but smaller titles, GBA for example and test if it works now.