Note: This applies only to those with a 50-Amp EMS unit.
Progressive Industries has added an additional test to their EMS50 units to look for those cases where both "hot" lines are from the same phase.
When this condition is detected, either from pedestal mis-wiring or thru use of a "cheater box" (or just from using a 30-amp adapter), a new code is displayed which let's you know that current must be limited to 50 amps total on the two legs.
The current is then monitored and if the total value exceeds 50 amps, power is turned off to your RV (for 4 minutes) to allow you to turn some appliance off to reduce the current. (An E11 code is displayed when this occurs.)
Availability of new units with this function depends on what's in the supply pipeline of course. They tell me that they will be happy to upgrade older units for anyone who asks. ("Upgrade" means that they ship you a new circuit board to replace one of those currently in there, and it is up to you to install it.)
Here's a scan of the instruction sheet that explains this new function.
Refer to this older thread for discussion on the need for this function: 50 Amp Service has to be 240v