Biggest danger is rubble being stuck in the tracks and roadwheels/drivewheels. In particular any metal.
I remember a story form my time in the german bundeswehr of a modern leopard 2 tank getting stuck, while driving accidently over some old, rusty rolls of barbed wire. Four leopard 2 dashed through an thick hedgerow in which some old rolls of barbed wire was still layed out. After some driving forth and back the barbed wire roled up around the drivewheels of one of the tanks and completey jammed one of the tracks. One out of four tanks was just immobilized by driving over old, rusty barbed wire.
Now imagine a tank with a building collapsing beside it. From all directions rubble, wood and metal falls and slips into the roadwheels. While maneuvering the rubble moves and makes its way deeper and deeper in between the wheels. Eventually the tank is stuck.