Please help with wind and grass

I’ve spent days trying to get this working. I can’t post a scene (it is literally huge, and includes paid for assets - particularly the grass asset).

I have three particle systems on a “plane” (it’s actually a subdivided and flattened landscape object). One is grass, one if dandelions and one is hyacinths.

Now, for the sake of speed, I bake each separately, with the other two turned off, though this is probably not relevant.

The particle systems are hair particles, with collections as render objects. Hair dynamics is turned on (and is obviously working, read on).

I have a wind force, which is intended to give a gentle breeze effect across the grass. Not a long anim - 250 frames. The dynamics are obviously working, since when I bake it starts with a breeze effect, but this dies out before the 250 frame end. It shouldn’t. I think that what I am seeing is the particles settling, and the wind doing diddly squat.

I’ve tried keyframing the wind force, from a strength of 1 to a strength of 50 (which should be a gale by then), but it just fades as the anim progresses, suggesting that wind is doing nothing.

I’ve tried replacing the particle objects (from botaniq replaced with grass essentials) with no change. The weeds (dandelions and hyacinths) are more convincing, but I think it’s simply takes them longer to settle.

I have a turbulence effector, makes no difference.

I’ve added a noise modifier to each of wind and turbulence. No effect.

What do I need to do to make the wind work?

For what it’s worth, from old fixes, I have the hair set up for dynamics.

Screenshot_2021-10-09_16-50-30

What may I be missing?

Blender 3.0 - 439c9b0b8478