I was trying to scan/tag a large music album (about 4000 FLAC files) but after an hour or so, the picard window disappeared and I saw the following error in dmesg:

traps: picard[31914] general protection fault ip:79ef823c7ee4 sp:7ffe4566e648 error:0 in libQt5Widgets.so.5.15.0[79ef82395000+3af000]

I had simply added the folder to picard, selected all the items in the left pane, clicked the Scan button (no other program or operation in the background), and the program was correctly retrieving the metadata before the crash.