Yes, they are simple straight extrusions up from simple 3rd degree curves.
Glad to have found something on time.
I also am experiencing Viewport display issues - CP points not showing up, can not select them. and even show them up bu pressing F10. X-ray mode, curves not showing properly. (in the options all elements have ticks checked). I do not know. Quite strange. Maybe I have made some tweak (to the default states) and now can not remember what it was to revert it back.