Hi everyone,
I just finished a game and a little situation came up where my friend and myself ended up in disagreement. I was hoping if you guys could help out..

I finally dared to try a Hemlock wraithfighter list with lots of pinning and 2 x hemlocks..
At one moment I cast my terrify power targeting his CSMarines, he failed their morale test and the unit fell back (close to the table edge)...
In my shooting phase i shot down more than 25% of that unit and since this triggers another morale test he should automatically fail the test since that unit is already falling back. (rulebook pg. 30.)
I insisted that they should make another fall back move off the table (The rulebooks says that units make a Fall Back move immediately upon failing a Morale check) but my friend claimed that it would be logical if there was only one fall back move per unit per round.

We played it my way because it seemed RAW, but since this won me the game I wanted to make sure if we played it right.

My friend explained that it doesn't make sense because this way we could force a unit to fall back 6 times per turn (for example if we had 5 psykers with terrify in range [3 hemlocks & 2 farseers] + the shooting phase 25% morale test) with an summed up average fall back distance of more than 40"..
The argument: Infantry should not be able to cover such a distance in one turn.

Thoughts?