Pump propeller spins wrong direction

I own a CTX Typhoon pool cleaner and the pump I believe is the same that is used in some aquabot models (P/N: AS00035R). The isse that I have is that the pump has stared to spin in the wrong direction, thus water pulls into the unit instead pushing out of the top. It seems like the polarity in the pump motor would have change. I have checked cables (from transformer to motor and from motor to pump) and they seem OK. Motor also works OK. The pump is apparently sealed (never been oppened).
Could anybody help or give any tips on how to fix this issue?
Any help will be greatly appreciated.
Many thanks,
Miguel