Thank you, all of you, for the helpful suggestions. They did change threads. I had planned to take the same type of thread I always use.
Getting a new bobbin case is not an option in this area, nearest dealer is quite some distance away and does not stock bobbin cases as a routine item.
The needles they are using are the spare ones I sent (they don't fit anything I have now).
Their problems began when they changed threads and put a project vs practise sandwich on.
The frame is level, in fact, it is more level than when I had it set up in my room.
I'll keep you posted!
If anyone thinks of anything not already suggested, please post!
Thanks,
GEMRM