Only 50 runs all outlets

I've been camping for decades and this is a new one for me. Just purchased a 2012 KZ fifth wheel with 50 amp service. When I first purchased it and plugged it into my house service via 20amp connection, all the outlets and devices ran properly. Then one day, only half of the outlets worked. Figured I messed something up UNTIL I camped at a campground with 50 amp service. Plugged it in and all was well. All outlets and devices worked. Next weekend I camped at a place with only 30amps. Plugged in using the appropriate 50am to 30amp plug and ONLY half of the outlets worked again. What is going on? Thanks!