Sequoia 15.3.2 does not preserve screenshot preferences

Environment: M4 Mac Mini Sequoia 15.3.2

Using the same keyboard combo Command-Shift-5

Untick " Show floating thumbnail "

Restart computer

The preferences above remain UnTicked

Try a Restart in Safe Mode.

This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts.

The boot up will be slow and can take some time - Normal.

Safe Mode will also eliminate Third Party Software, extensions and drivers from loading.

It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 

Does the issue present in this mode ?

Sometimes a Safe Boot followed by a Normal Boot will just put things right.🤞

This could be due to a corrupted plist file.

Try this:

1) In Terminal, paste the following line:

defaults delete com.apple.screencapture

2) restart (all settings should revert to their defaults)

3) set everything the way you want

4) restart and your choices should persist

You are welcome