Reavers chasing fleeing units.

Hey mates, please confirm the thought if i havent missed anyhting rulewise.

Imagine situation - we tank shock enemy and he fail morale check and flee.
Then we hit him with Reavers BladeVane atack. In Movement Phase. We do 25%+ kills of targeted unit.
At any phase if the enemy lose 25% of his unit he is forced to do another morale check, which in this case he fail automatically cause he is already running. So at the end of the movement phase he must run again.

If we completely surround enemy unit with Reavers and possible backbone skimmer and he cant retreat again does that means that unit is trapped and destroyed?

I belive you fulfil the trapped requirments as the unit must double back and thats a no no