are you using the correct equipment during the correct seasons for them? I tested and they register on my end.

Its how the game engine works with the field definition to "cut" out the wetlands. Some fields it'll work fine, others it just bogs out trying to run the algorithm bc theres too many boundaries and the ones where the field is cut in two by a stream or wetland it'll crash. I would recommend EV and autodrive mods in lieu of.