When is a Medium tank a Heavy tank?

[Dan Caviness]

Fellow Grognards:

In laying out my new scenario in the Carpathian mountains I noticed that a captured German Panther tank for the Russians cannot cross a medium bridge while the German version of the Panther can.  So it's a glitch but it's a bitch of a glitch and I for one love to bitch.

I was wondering what the Soviets could do to a Panther to make it become a heavy tank?
Any rational explanation out there?
Or is it just a mistake/glitch?

Regards,

Dan