I have two contenders, a original and a new G2 and ca't say I know what the problem is but this is what I would check first if I had your situation. Only do this if you are comefortable with diss and re-assembly of your G2.
First I would want to know if this happens only after firing a round or if it happens when opening and closing the action without a round in it.
If it happens after firing a round that might be a result of a problem with your firing pin assy. If it is bent or broken or the return spring is damaged in some way it could the firing pin to stick out into the dent in the primer pocket and cause problems opening the action. Are you getting any draging marks on the primer when you do get the action open? That would further indicate a firing pin problem. To get to the firing pin you will have to completely diss-assemble the action and remove the slotted screw in the frame in the hammer notch that holds the recoil plate in. Again, if you have never done this to a G2 putting themback together needs to be done right and is tricky. Was the screw holding the recoil plate tight when you went to remove it? I had one of these shoot loose years ago and the loose plate tied the action up in a similar manner to what you described; but this would happen on a empty chamber also. Inspect the parts and replace any damaged and re-assemble and give it a try. If close inspection does not show any damaged parts I would then look next at the locking bolt in the underlug of the barrel.
TC has has several different versios of this bolt and the later split version has a tendency to break. To remove the locking bolt drift out the roll pin holding the locking bolt in. This bolt is under spring tension so make sure to keep pressure on the bolt to keep parts from flying out and do wear eye protection. If either of the bolh halfs are bent or broker call TC and they will send you a replacement probably at no cost. If no problems, clean everything, lightly lube and re-assemble and give it a try again.
If you are interested in detailed instructions on how to take a G2 appart and put it back together Mike Bellm has an excellent tutorial with great photos on his web site, just Google him for his site information. If non of the above solves the problem you can also email Mike for help which he freely provides. Mike Bellm is probably the most knowledegable TC gunsmith out there.
Good luck and let us know what the final solution was; and stop shooting excessive loads in your Contender!