Hi Cliff,
no idea how to reproduce this one, sorry 
The first pic is a close up of my exhaust installation module - which seems to have a side window in it’s stockpile.
The second pic is the main production line, showing exhausts and windows, with no crossover between their installation lines/import lines or anything else i can see - and there has never been cross over.
not sure if this is a visual glitch or something else.
Regards,