Moodle: Cannot delete H5P activities

Hello, We've just started using H5P after trialling it on a single interactive video but in testing out all the content types we found we are unable to delete a H5P activity.

Moodle lets us delete it, but if you leave the page for a while (about 60 secs) you get an modal box saying 'Error: Unknown Error'. You can then refresh and the activity is back! Likewise if you navigate away, it tries to load the new page and after it times out and we get a Error 500 Internal Server Error page. Then if you go back to the page, it reappears.

Using Moodle 3.1.5 and yesterday upgraded from 1.6 to 1.7 (was hoping the update would fix the problem). Our moodle is hosted by our vendor partner but they consider H5P a custom plugin so any support will cost money. FYI, the attempt to delete isn't showing in the Logs.

Any ideas on what is happening or other experiencing the issue? Otherwise we will have to move away from using H5P, which is a real shame.

Thanks in advance.