Q&A crashing site after updating to WP 4.5

NOTE: The problem plugin is Q&A but since it has been disabled, it does not show in the list for selection. I have had to select SOMETHING so selected the dashboard.

I updated this site to WP 4.5 this morning. No issue. I then selected 'Upgrade network' and instantly got a (Litespeed) 503 error. After investigation, I started testing plugins. After disabling Q&A the site recovered. Reactivated Q&A and the site crashed again. Disabled again and the site recovers so there is no doubt Q&A is the issue.

I have moved the plugin to a directory called plugins.disabled

Please advise a solution.

David Wilks