Batteries

I had a similar problem. Mine however was the transfer switch cutting in and out while on shore power and connected to a 30 amp breaker. 50 amps seemed to w0rk fine as did generator power. The problem was finally identified as a bad plug on the end of my 30 amp extension cord. I suppose it could just as easily been the plug on the 50 amp main power cord but in my case it wasn't. I think your problem may be the same, or if the power cords are okay then it is the transfer switch. I say transfer switch assuming that your ems unit is not showing any codes to indicate that it switched off and on due to low voltage etc.