It usually renders to pdf (bitmap mode) like this (these are solid fills which display as even tones in print display, but they print with an unwanted grid patten overlaid):
Also a solid hatch with all attributes “by layer” will often persist in the colour of the layer on which it was created rather than the layer to which it has been copied.
Sometime a new hatch on a new layer will become the colour of the transparent layer on which the last hatch was created, thought it’s being created on a new transparent layer of a different colour. Sometimes that can’t be changed a new one has to be created on the new layer.
Sometimes a hatch will print with the colour of its originally created colour though it has been copied to a new transparent layer and displays with the colour of that layer.