The problem is caused by a script which is not working properly for a grating in the process. You need to delete it.
Open Drawing process manager and go to the drawing style you need to use.
Open the properties for the "Drawing style map" and scroll to the "Model Object" : MP - Plate. Open the script option (the column for scripts is on the left of the "Model object" one and delete the whole script. In addition, please change the MP - Plate model object to : Mp - Grating (this model object is found in the "Main Parts" category).
Now this process will work and detail gratings.