Google sheets blurry on Safari - tried everything.

When I use Google Sheets on Safari, the content of the spreadsheet is blurry. The rest of the page is fine (toolbars, etc.). Screenshot here

Here's the frustrating part - when I load the webpage, the text is completely sharp for a second or two. Then there's a yellow box at the top of the screen that says "Working..." and the text then turns blurry - as if some CSS was being applied.

Notes: Does not happen in Chrome. I've tried clearing cookies and website data. I've tried disabling all extensions - no change. I've tried disabling Javascript - Google Drive no longer works. I've restarted browser. I've seen a few other people comment on this problem online but I have not found a fix. Changing fonts does not make a difference.

Any suggestions? It's driving me nuts.

Thanks!