Depends greatly on power distribution within the park after it leaves the transformer and runs thru the main service panel.
It can mean one of the legs is not getting sufficient voltage from the transformer (electrical Co. problem); it could mean too many RVs on a marginally size wiring setup; also possible the park needs to attempt to "balance" their 30-amp panels by switching customers from the high circuit to the weaker circuit; and a few other possible situations causing it.
If it were my park, as owner, I would put my meter to work and trace the low voltage from your pedestal all the way back to the main service panel, if necessary. If one leg is low coming off the transformer the power company should send out a service crew to check it out.
If I were you I would use, or purchase, a multi-meter and check the voltage myself at the actual pedestal plug (both circuits). GFCI panels are great, but can be temperamental at times.