Are you using the LONG DOGBONE type Adapters going from the 10-gauge extension cord to the RV Side.
If you are using those small round type RV adapters that might be source of the voltage drop.
I cannot use these types of RV ADAPTERS
I run 50-foot 10-Gauge here on a 20AMP Garage Circuit circuit for my 13,500 AC and it works great with just a few VOLTS DROP.
If you have been using the small round type adapters you may have already burned the cables plugs already. Check them out for burn discoloration...
If they look like this google photo they need to be replaced now - this also will cause VOLTAGE DROP big time.
Anytime we have long cables hooked up will check the connections for heat after 10 minutes of operations or so. You can usually find a hot spot fairly easy doing this...
Roy Ken
