I have a 20 gauge Baikal IZH 27EM-IC over/under that won't open. Pushing the lever to the right used to allow the gun to open, but now the lever won't move to allow the gun to open. I tried applying Brake Free penetrating oil where the lever rotates and waiting several hours to see if it would free up the lever to open the gun, but the lever still won't budge. Does anybody know the cause or how to fix this problem?