Mac OS Sequoia 15.0.1 - next bug -- FINDER

In Disk Utility>View, select Show all Devices, highlight the top left entry.

Run Disk First Aid on all items in the left panel, from top down.

Are you running any VPN, Anti-Virus, or Cleaning apps?

We need to see what all is running, a report from this will not display any personal info...

Using EtreCheck - Apple Community

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info. Give it Full Disk Access.

https://www.etrecheck.com/

Give etrecheck Full Disk Access before running.

Thanks for Old Toad’s etrecheck instructions…

Slow iMac 2017 - Apple Community

I noticed that if you open an mp4 file in Finder with the space bar, and you make it to full screen and you want to fast forwarding it with two fingers, the video will freeze. Then it can't be played anymore even if you go back to not full screen mode with Esc. To be able to play the video, you have to close it, and start to play it again, and avoid to do the above written things. It is very annoying to me because I used to watch videos like this.

Make sure you're not accidentally closing them by clicking the caret…

Then I don't know. My favorites have never disappeared on three different Macs running Sequoia.