I was having this issue myself and I'm on a 13700k with RTX 4090 and 4tb Western Digital Black SN850x NVME Drive. I don't think its a hardware issue or drive issue. So I did some testing and think I've found a fix. Thought I'd share my discovery if it helps anyone and hopefully the developers can pick this up and possibly fix it.
So after trying just about everything I thought maybe it's got something to do with the file sizes, possibly even if a file is jpeg or png. What I did discover is that for example on NES, if you scrape your games in like normal, the box size dimensions (you can right click the file, select properties, details tab, scroll down you will see resolutions etc.) are very big. Some of my boxes were 5000 pixels in width. So i used an app called Faststone Photo resizer and decreased the box art down to below 2000 pixels but while also keeping the aspect ratio so it doesn't mess the file up. So same box just smaller in size. When i went back to big box and selected that game which always lagged and wasn't smooth on animation guess what.... Smooth as butter. So I think some of the art being scraped is way too big and it just can't load it in quick enough to animate smoothly. Reducing the box sizes on my entire system fixed all my issues. I'm also running 120hz mode too.
If someone can test this out on a system you are experiencing this on and report back I think it could be fixed.
Only problem i'm facing now is I have 28,000 plus images to look through and reduce resolutions on. Bit of a task but so far I've done 3-4 systems and they all animate smooth now with no problems.
