hi people, have sold quite a few tigers,and have just taken delivery of some of the panzer III and sturmtigers,i always check all the tanks before sending them out and have found a few ways of fixing them that maybe of help,firstly if the gun doesnt fire/shoot or move ,on any of the tanks i tend to think it is a remote control problem,i normally try another but know not everyone has this,the cure can be to take the control apart and undo the 4 screws on the front that hold the stick in place,gently release the stick and you will see the at the top and bottom a little metal part the makes contact with another matal part(hope that makes sense)there is one on the left and another on the bottom,you can try pushing the stick and gently pressing the metal part to make a contact,if it works that is the problem,the is a little screw to release the part,undo it and gently bend the arms down a bit,put it back on and try it again,
dont know if this will help,also for tanks that go fast on one side alter the plastic sliders on the right hand joy stick this will stop the tank moving forward or back ward,or the other slider will alter the left or right movment on the motors
as i said before hope thos helps and makes sense