Final Cut Pro crashes on export

HI all, I'm on an iMac, 27-inch, mid 2011 machine, running Sierra. My FCP is 10.4. This past week I updated iTunes and installed a security update. Now, Final Cut Pro and also iMovie crash when trying to export/share out a file. I'm unable to update FCP any further without buying a new Mac.

Things I've tried in both FCP and iMovie:

Restarting.

Creating a new event and/or project from scratch.

Tried sharing/exporting in every way possible.

I would be grateful for any help as nothing is working.

Best,

KD