How to troubleshoot broken theme

Hi

I can no longer edit products (the product data fields do not show in the dashboard).

I went through a checklist and I have found that if I switch to a standard theme it fixes the problem.

Only things now is I don’t know how to troubleshoot any further.
The theme was a custom one and I’ve used the beaver builder plug-in to make further customisations.

Any suggestions on how to begin troubleshooting the problem theme?

Regards
Andrew

PS – On the product dashboard I the ‘screen options’ tab won’t open either. Doesn’t appear to be any javascript errors in the console.

The page I need help with: [log in to see the link]