"remindd" cpu process will not stop: macOS Big Sur 11.5

Does this issue present while booting into Safe Mode (Shift ) immediately at restart and hold until Apple Logo is presented and release. Does a Repair Disk, clear cache files and only loads Apple Software, extensions and fonts. So, loads slowly - normal. Once logged in - run this way for 5 - 7 minutes and check if the issue is present. If No - there might be some third party software interfering or could be an issue in the User Account.

Set up users, guests, and groups on Mac and Test

Same issue—on a 100% clean install of Big Sur.

The Reminders app has been an abject failure for more than a year now—it's hard to believe that a company of Apple's size and resources can't get a simply to-do list to work and sync properly. I had ghost Reminders, ones that only showed up in the iCloud web interface, which didn't allow them to be deleted, ones that spontaneously disappeared, and scads of other weirdness.

It's also beyond me why it's not integrated into the Calendar app—everyone I know uses a task list and a calendar at least a dozen times a day, and their functions overlap. I just don't get why we're getting Animoji and Spatial Audio—both great functions, in their own right—while Apple's integrated task list doesn't work.

Recently, the sync of Reminders seems to function, somewhat, but the remindd process hangs up the system. The only solution I've found is App Tamer—an application that can limit the CPU usage of individual processes.