SafariBookmarksSyncAgent stalling Safari

[Buckskin]

I've been having trouble with Safari stalling on startup and when I quit out. Both stalling events can last minutes. I can force quit and try again, but the stall returns.

In frustration I began running activity monitor. Lately I've noticed that every time the stall occurs, SafariBookmarksSyncAgent is running. Further, it is consuming large amounts of CPU, Disk and Memory resources. If I force quite it, Safari resumes normal operation.

I've turned off Safari iCloud synching, but that has no effect.

Any suggestions on what I can do to bring this under control?

 

[bogdanw]

Unfortunately, when I’ve tried to disable SafariBookmarksSyncAgent in Big Sur, Safari wouldn't quit.
But com.apple.SafariCloudHistoryPushAgent can be disabled without any issues.
From Terminal

launchctl bootout gui/501/com.apple.SafariCloudHistoryPushAgent
launchctl disable gui/501/com.apple.SafariCloudHistoryPushAgent

To re-enable it

launchctl disable gui/501/com.apple.SafariCloudHistoryPushAgent

and log out/restart.