I bought one from rctank.de too. I guess it's the same version with mine so here is my comment.

1.The BB red light will permanently on if the recoil unit didn't align properly and will cause the tank run incorrectly or don't run. Check your gun barrel position. Try un-plug the wire to upper hull and start the tank. If the tank run then the problem is what I told. I had this problem twice when I shot the gun and battery run out so the gun stuck inside the turret before release out.
2.Don't use glue.The road wheel attached to swing arm by a small grub screw. You may lost the screw already. Carefully check the swing arm.
3.The track is too long. I took out one link from each track. It runs better but still have to take out another one from left side. The spring in my left idler adjuster seem softer.

Hope this help.

I re-painted mine using 1/35 box as reference. She runs great.