I have this same problem when I'm not careful while doing my flips. My guess is that you're bogging the rotor, in which case collective management is the answer.

Going full negative while at a steady hover means that the blades only hit 11 degrees or so of deflection. No problem. Add to that full back cyclic for a flip and your blades will hit upwards of 18 degrees. This causes the rotor to bog which means that you lose tail rotor speed and, as a result, tail control. This is one thing that simulators don't seem too good at replicating.

So, go easy on the collective and I think you'll have much better results.