Thanks for your post. I would have answered last week but was on hols.
The problem you describe is exactly the same as ours. I first reported it to VM during November 2021 but it has not yet been rectified and it happened again today with a series of incoming calls from two Virgin Mobile callers. Some time ago, I even went to the lengths of setting up trials with three Virgin Mobile users to provide data to help VM diagnose the problem. It seems to me that the problem is within VM's system with communication between the bits that service their mobile network and the bits which service their landline network. We never get problems with callers from landlines or from non-VM mobile callers. For example, I have a 3 mobile and it calls our VM landline faultlessly. Similarly, my wife can call from her BT mobile with no problem whatsoever.
It is interesting that you report crossed lines with doctors surgeries. We have had a similar experience with doctors surgeries and veterinary practices although we have also had a variety of crossed lines with people trying to make appointments with opticians and local councils. Sometimes we (or the caller) can talk with the crosser but often it seems that they cannot hear us and soon hang up.
Regards ...Robert