I have the same problem, on OSX 12.1.
There are some related reports:
I found that this tool is able to recover (some? all?) the ...
Thanks for the answers, for me the thing that worked was to reset Preview and then restart the OS. By resetting the Preview app I mean to delete all plists and caches.
Also few suggested to restart Finder, when I do that my whole system hangs and I cannot do anything, not even shutdown/restart the OS, I have to resort to forcefully killing (shutdown) the ...
Preview inserts a check mark and I’ve not found any way to change this.
If the check box is correctly presented as an interactive element in the PDF, it can be set to use an X-mark, but this is to be defined in the PDF itself. (Then there’s sometimes a bug where both are inserted: Strange tick mark in Preview.)