Thanks – how silly of me(!) But that’s what happens when things have been left for a while without needing attention. Got into Thinkific and sorted it all out.
Additional Information:
The problem occurs on a PC running Windows 10 and either Firefox or Chrome browser. Have just found that it DOESN’T appear on an Android mobile device(!)
Already posted there but the behaviour seems most likely to be caused by WP itself – otherwise a Theme rollback would have solved it.
