I hope you put in two new corona wires in the primary. Sometimes this machine likes all its corona wires to be new. Not grid, but just the coronas and then it can be happy. If not I have seen some unstable quality issues, and or the machine wanting new corona wires in the primary too often. This is esp true if you are not using the cleaner pads on the corona wires. Some people who cant see good just chuck them off.