I have an EM, Gottlieb Super Spin that I sprayed many years ago- using a high quality true automotive 2-part clear coat (DuPont high solids urethane). Its as good as the day I sprayed it and easily a thousand plays over 6 years or something. A good quality clear is absolutely not expected to crack. Quality is crucial. The good stuff is over 500 a gallon when mixed. Many people save money on clear coats or use rattle can “clear coat” and you do not get the same performance. My experience- not a pro. I have sprayed over 5 playfields and other projects. Never had an issue. Your Mileage May Vary as the surface prep, mixing, spraying and coat thickness etc all are hugely important. It costs a shit ton to do this right. Its worth it when done right. Plenty of horror stories playing out now to demonstrate that its also not trivial to do this correctly.