At least your Sherman didn't teleport into the Vineyard and become immobilised. Which is what happened to me on the three occasions I have witnessed this bug.
Agreed the chassis were still in service, but the OPRA was a 105mm armed Centurion MK.13 with added laser range finder and various optics and sighting gear on the turret roof.
The only Centurions still in British service in the time covered by the game, were operated by Royal Artillery Forward Observers, and known as Centurion OPRA. By 1980 there were only a handfull still in service.
Land Rovers didn't appear until the early 1950's, seeing service in the Korean war. SAS Jeeps in WW2 North Africa were stolen from an Egyptian dockyard.