Imac 17,1 running Catalina 10.15.7. Working fine until Safari (15.6.1) is opened. Then it's brought to its knees. 20 secs or so, it operates at full speed, then for a minute or so, I can move the mouse across the screen and it will take 10 seconds for the cursor to catch up. Cleared all caches, followed numerous how-tos, but it persists. Is this a known issue, can I delete/re-install Safari? At my wits' end over this!