This isn't likely to be normal. It indicates a possible bad connection between 30 amp plug and pedestal; or a loose bad connection at the 30 amp breaker in the camper. Check the plug for indications of over heating, the same for the socket at the pedestal( that is up to the CG to fix the socket). With the shore power cable disconnected from the pedestal remove the cover from the distribution panel in the camper and inspect the connections to the 30 amp breaker and the neutral wire to the distribution panel. Since the distribution panel in the camper has 12 vdc you may want to disconnect your battery first. This is just for starters.