I've done quite a bit of testing, particularly with trickled charges.
Electronic scales that were not designed for reloading do not respond well to trickled charges, or light charges.
I'd suggest that is a big part of the problem, right there. Possibly because they don't take into acount the fact that the object being weighed will have a slowly & constantly changing weight when trickling.
Allan Quatermain: “Automatic rifles. Who in God's name has automatic rifles”?
Elderly Hunter: “That's dashed unsporting. Probably Belgium.”