pro 5100s - by pass DL envelopes JO98 paper thickness error ?

[Jedi Ben]

Hi,
we have a printers using DL envelopes which are brown (like budget toilet roll) 80gsm which always stops over the ptr roller. J098 code. they use the original template on the flatbed glass> copier > by pass.
my try's:
used all paper weight settings within the copier by pass - still jams
used the correct paper size envelope DL and user tools paper settings - still jams
used the custom size option and inputted the correct sizes of the envelopes - still jams
tried the envelopes in tray 3 + 4 that jams - same place even though its using the vertical paper weight/thickness sensor.
i even turned off the the both paper weight thickness sensors in sp mode - still jams
i have extended the call for parts for a paper weight/thickness sensor for the reg/ bypass path and ordered a new registration unit as its mylar guides ect are shot but they are not causing this issue. i get other jams from snagging which for now i cut bits off there mylar to get tray bottom trays going.
As always the customer states we done this job on the same envelopes last year fine. i asked are they defiantly the same brand and supplier - yes.
i have looked at the media library for this machine and it is stating 120g or a 135g - so im presuming they should never use 80g but there argument is - why can i select 80 gram as the weight in the user tools paper weights
any help on this one would be very much appreciated. as they have 4000 to do on them envelopes
i have got our office to purchase 120g white envelopes to see if they go through set at the correct size and weight.
i have also looked at the user guide for correct loading in the tray
thanks
Ben

[slimslob]

J098 is a paper thickness error. Might be a problem with the bypass thickness sensor.