Can't change APFS drive icon

Okay - this is a weird one...

I have not been able to change the Desktop drive icon for one of my external drives since Big Sur.

Background: I have changed all the other drive icons (even another drive in the same enclosure). If I copy and paste the icon from another drive (where it displays correctly) using Get info, the Preview shows the change, but the drive icon at the top is unchanged. I have restarted Finder, restarted the machine, tried multiple processes to copy and paste - keyboard, mouse command-click, using a third party clipboard utility, etc. No change. I have selected "Ignore Permissions" for the drive - no luck there.

Drive Utility shows the "correct" icon for the System volume of the drive, while the physical disk, APFS Container, and the Data drive all show the old icon (the default butt-ugly yellow one).

Attached are the info panels for the drives on my desktop - it will be obvious which one isn't playing well. I am beyond what I know about the OS and its inner workings at this point. Any advice is appreciated.