Unfortunately, due to a "family emergency", I can only respond today and thank you for the numerous and helpful tips and ideas.
I will go through them all, evaluate them and then report back to you.
Tim
PS:
Roland Jaeckel had another very promising tip: since the springs of a Pantera usually don't get tired, or only very rarely, he suspects that the lower axle of the wheel carrier could be stuck. I haven't even considered this yet, so I'll check it first. That would be a relatively simple matter....