Cannot empty trash v 5.6.3.3

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Can anyone help me with why one of my sites is having a problem with emptying the trash?

I am using 5.6.3.3. on several sites and can empty the trash on all sites except one. On that site, the loading icon keeps spinning. I stop it after 20 minutes, b/c it seems stuck.
1. I try permanently deleting one page at a time - get spinning icon and page does not delete
2. I've cleared the cache
3. I am using a different theme (Foundation 5) on this site, but I doubt that is the problem
4. There is an upgrade to 5.6.3.4, but the earlier version is working on other sites. Plus, it's an active time for the owner and their clients visiting the site - and I don't want any problems (even though I have current database and site backups)

Any ideas?
Thanks!

webadminfl