I have noticed a weirdness regarding the saving of AcoustID tags.  The AcoustID tag only seems to get (newly) set on files if a "Scan" operation is run on them AND the lookup of the fingerprint is successful.  However, if the files were manually moved to their positions in the right hand pane (either because "Scan" was not run or the AcoustID lookup fails), the AcoustID tag does not seem to get set, even though the "Generate AcoustID Fingerprints" operation has been run on them.

To me, this seems like a bug.  This has been biting me a lot lately because the AcoustID lookup service seems to have been unreliable/offline pretty often recently, so I've had to turn off auto-scanning new files to avoid excessively long request timeouts and failures.  And if either the scan isn't run or the lookup service request fails, it doesn't seem that the AcoustID tags are getting saved in my files even though fpcalc has been run on them.