Regarding the Panzer, I've yet to see him go invisible, that would be terrible, nor have I had any issue with the robots, from experience, I think the lights on the foot switch at random, but shooting them has never been an issue.
Also the tank pushing you off...strange there would have to be a clip of some sort to make you be pushed off, there really is not other explanation other than maybe perhaps a model was loaded improperly and was in the air invisible, I remember on Tranzit, seeing the towns bricks not load into the walls correctly, they would float in the air around the stop lights sometimes.
The zombies running faster from a result of the tank is common, and if they are increased at all in speed, it's not by much. I deal with this all the time, it's just their animation is stuck to the way it would act if you were on the tank, I believe the speed corrects itself but the animation doesn't.
The only one I've ever seen, excluding the running zombies, is the death by tank, I have no explanation for this but I only see it so often.
I would say MOTD or Buried would be buggiest game of all maps, as of now, I can't even play MOTD as it crashes on start up (many are having this problem still) and Buried just loves to crash when I get a bunch of money out of the bank.
On Treyarchs defense, they are not really given much time to make these maps, so it's kind of just playing by ear as they rely on the community to bring up the issues that need fixing. Not to say time is everything, they had, I think, two weeks or so to make Ascension and it's still in my top 5 maps.