Shifting issues after battery replacement

I had my battery replaced by a repair shop on my car and about twelve hours after the car began shifting in to second and fifth gears awkwardly. About three hours later the mil came on. I took it to the same mechanic and the said is was giving p0340 code so they did fuel induction service, air filter replacement, mass air flow and cam shaft positioning sensor cleanings as well as oil change. They told me problem was fixed but as soon as I got in it started again and they said CMP need replacing. After researching I discovered loose battery connectors could cause the same code so I checked and sure enough half of the connector was above the terminal on the negative side. After repositions and tightening the mil went away and problem stopped. I started my car again about five minutes later and both were back. That has been the case about five or six times of disconnecting the connector. We also discovered that the connector is easily movable even when tightly closed. Could this be the cause of the one code? Also, could the ECM be damaged from the continuous driving with a loose connection?