fonts in mail are f'ed up since upgrade to Big Sur

Hi SirSpinach1,

Thanks for using Apple Support Communities. We can see from the photo that your email fonts aren't showing as expected. We certainly want to get this resolved for you, and we're happy to help.

We recommend restarting your Mac in safe mode and then testing if the issue continues from there. You can see how to restart in safe mode, and the steps to take if the issue does or does not continue there in the resource below.

How to use safe mode on your Mac

Thanks.

The only activated versions of Arial in my Suitcase are system fonts and are locked. I used "Inspect Element" to turn off the font styling for gibbled text in Safari, and the text turned legible (but not Arial... Maybe Georgia or Times?). The problem also went away when i forced FMCore to quit in Activity Monitor. So it's definitely a problem with Arial, and maybe related to Suitcase, but I have no clue how to resolve it. Help!

I have had this same problem since upgrading to Big Sur. I've tried validating fonts and restoring standard fonts in Font Book. I've removed caches, disabled Suitcase Fusion, reinstalled the OS, etc etc. Some fixes have worked for a few minutes, but it always reverts back to text replaced by question marks in Mail and Safari. This is a ridiculous problem to have on what are supposed to be the best computers out there. I wasn't even going to do the move to Big Sur, but I was getting sick of the pop-up reminders multiple times a day. It amazes me that Apple would release an OS with a fundamental flaw like this. So far the only option seems to be to go back to the previous OS and hope they fix this issue in Big Sur before trying again. It doesn't fiil me with any kind of confidence.

The below screen shot was taken after trying every solution I could find online. This is a major stress and a juge waste of time for someone who uses their computer all day for work.

So I've noticed that this problem goes away when I restart my computer, but comes back within a few minutes regardless of whether Suitcase is running or not. It also looks like the font that can't resolve is arial which is a pretty standard system font. I guess I can disable the variations of Arial in Suitcase and see if that fixes things...

Yeah I've tried disabling Suitcase and it makes no difference.