It is good to have testers with you to check the power at pedestals. However, the readings would depend on what you would expect. Readings could be within normal limits as shown on the tester but this problem (loose neutral) could also happen in the coach, the extension cord or even the plug itself.
Anytime a 240 volt power is brought into the rig, there is this possibility--and consequently frying all your appliances.
This is the reason I don't want a 50A. With a 30A power feed, this can never happen because all you can get is strictly 120 volts. Others will not agree but the luxury of having a 240 volt that would run several appliances at the same time is an overkill in an RV. I would certainly enjoy all these niceties at home--not on the road.
Then again it's just me.