Modifying contacts triggers beach balls
Contacts app -on Catalina post upgrade to 10.15.5 I think and now on Big Sur - going into beach ball any time I edit or delete a contact.
my contacts are on 2 clouds , pro and personal, for a total 15,000 or so
i am running iMac 27 2020 so the hardware is not the issue. I suspect interaction with Mail could be the issue.
2011 macmini running high Sierra and the contacts synced to the pro cloud does not seem to have the same issue (not running Mail though)
i reported the problem to apple support but they were not helpful .
iMac Line (2012 and Later)