Were the REV indications only present once airborne, or did they show during the takeoff roll? It could be that the inboard and midspan LE flap groups retracted during the takeoff roll, but then re-deployed once the gear tilted as it got airborne?
The auto retract of the l/edge flaps is only armed on the ground. Therefore when the aircraft became airbourne this signal from the Thrust Reverse relays would have been lost and the l/edge flaps would have deployed again.