[Janz]

Yeah, had that happen to me too. Did a nifty counter attack, picked off all the enemy and then headed for them mortars.
Took them out one by one but then after all is done - still no mission resolution?

And i mean i totally destroyed em...and all the houses..and cooked all the enemy tanks [or made em mine...yeah!]

The objective points [red arrow] to a non-existent mortar [you saw that too it seems]
I could not find the wreck at all...like it disappeared [hmm, i think they all did that, unlike tanks that remain in a damaged/burnt condition - but then some fade away tho mostly in co-op not in single player if i recall correctly]

I drove tanks over the spot, shot at it, piled all my [considerable] forces all around and on that spot, yet nothing.
No enemies lurking just off the map edges....
Took me at least an hour to play - enjoyable - but then a sigh and i just closed the game.

Eagerly awaiting a solution...good luck guys.