Sounds like either the seal on the popet valve is worn or the popet itself is rooted. Nope not normal, had this happen to me once, had a keg sitting in the kitchen over night, woke up in the morning to a beery mess all over the tiles, lucky I didn't have it sitting on the carpet, SWMBO would have tore my nuts off
I've had two leaking posts (1 beer, 1 gas) on my recent 4xkeg purchase. Both fixed themselves after reconnecting a 'disconnect' and then removing.
Probably wasn't sitting right. Another option is to relube the washer (if in good condition) with more lube. It seemed to work when I had a leaking valve on the pressure release valve.