well i have similar issue, on two macs now that i've completed the upgrade to sonoma 14.5 (yesterday for my m2 pro mac mini)
So if you have a finder folder with photo's and you set them to rotate randomly say every minute or 5 minutes, or so on, it always takes like 50 seconds or so after the next minute or next 5 minute on the clock has gone, for it to fade to the new photo, while in ventura it was spot on with the system time snap on each 1 or 5 minute or 15 minute or whatever interval