Hello I have 5K deye inverter hooked up to 3 parallel Felicity solar LPBA48170 batteries, once the batteries are fully charged the system just cut electricity from home for couple of seconds without any fault or alarm on the deye screen, it can happen once or 20 times in a row. 
What might be the reason for that?

If you have a multimeter, hook it up on the battery output. Check the voltage of the batteries when this happens. If batteries are supplying voltage when this happens, it could be that you have a problem with your inverter.