MG Car Repair: Pops out of fourth gear, mg midget, shift fork

Question
I just read a question you answered about an mg slipping out of third gear.  My 1972 mg midget is slipping out of fourth gear.  The former owner installed a rebuildt transmission and advised the car has done this since the transmission was installed.  Am I doing any damage to the car by holding the car in fourth gear so it won't slip out of gear?

Answer
Hi Mike,
You are putting extra ware on the shift fork. First confirm that the shift lever is not making contact with the shift tower cover and if it is not it can be several things that can cause one to jump out of gear but all are inside other than the shift tower.
Howard