I also add AcoustIDs to my files. And it is a weird process to do. Importantly make sure your files are already fully tagged up and it should cause less chaos when you drag them back over to the left side to click that Scan button.
Still be prepared to tag, save, drag to left, scan, drag back to the left again, re-cluster, then drag to the right, final save.
Often Scan will match to some other release even though you already have full MBIDs in the files. After a while you’ll get used to the pattern, but Picard is not designed for odd people like us who just want to add an AcoustID to an already identified file. 