Christoff is right - you can try to trim and see what difference it makes. If you are a bit experienced that is.
But I somehow have an idea you are relatively new ?
If so, it does not make much sense that it only happens in choppy water, if something with the foil.
And if it is choppy, you can not ride the board flat for long.
Would also think you "pop" it up too early and go too slow, so it stalls down again.
Eventhough, it should not if a fairly easy and lifting foil (how much do you weigh ? If a lot over average, you need much more speed before foiling)
Assume you have tried riding with the rear foot in front of the strap ?
As this helps when learning, but when better you somehow get more control and turning ability with the foot more aft.
If only in chop, it could be you, and not the board/foil.
Bcause you might instinctly, like naturally on other boards, try to follow the surface.
Try to look a bit further forward, maybe not fully at the horizon yet, but almost.
You have to ride straight through the chopwaves, of course foiling slightly lower in average than when flat.
This is way easier if your eyes are NOT focused on the surface in front of you - just a hint, try and see what happens ?
Just some ideas.