I have the same issue with the slow loading artwork. Only jpeg files as well. I ran the tests which all passed. I attached the test results below and a video if that helps determine if i'm just an idiot and this is expected behavior.
Crash when booting into OPL. Does not consistently occur. I am using an internal SSD. OPL and the config are loading from Memory card and there is a USB thumb drive connected though not actively used.