A while back I did a new conservatory and the fitters had sprayed the whole thing with silicone. I know they used that because the lady said they left behind several cans.
Cleaning it wfp seemed a nightmare as the water instantly beaded immediately after leaving lines over the glass.
I did a few panes trad and it just seemed to smear badly but after the glass had dried from using wfp, much to my surprise, it looked spotless.
Maybe it's the same problem?