MP C300/400 Image quality with Thick paper

[sandmanmac]

Saw something yesterday that I've not come across before, and looking for a little advice and enlightenment
I have an MP C300 at a church and while their volume isn't that large, they often print on different types of glossy or thick papers.
When they first complained about image quality a couple of years ago when I installed the machine, for simplicity, I told them to just always select "thick 3" and use the bypass tray for anything other than their regular bond paper.
When I went there yesterday, I expected that they were again, not setting the paper type correctly or something along those lines, but they were actually doing just what I had told them.
Here's what I don't understand, they were actually printing on 65lb stock, so the Thick 3 setting was the correct one for that particular job, but when it was printed there was a lot of background - especially on one side of the page.
When I used "middle thick" instead, the image printed clearly. (See samples attached)
Just for fun I also tried the same settings with plain paper and the results were exactly the same as on the thick paper.
In hindsight, I should've tried colour printing too, but my tests were only done with B&W.
The K-PCDU is relatively new and the machine has only 80K combined.
I feel like it must be an issue with the transfer roller which I'm going back with on Monday, but I'm hoping to get some input and explanations (if possible) for what might cause that?
Thanks!
Sample.pdf

[GIUBOSS]

stop printing before thick paper enters the fuser unit then see if the problem persists

[sanjiv]

Hi sandmanmac, you may try stop test, just perform as per informed by GIUBOSS. this performance will show you where exactly problem start. Fusing or Transfer Belt. Same time pls PM counter on PCDU K. PM count for PCDU K 60K.

Suspect on charging goes up when choose print on Thick 3.
PCDU K
Tranfer Belt

Thanks.

[sandmanmac]

Hi sandmanmac, you may try stop test, just perform as per informed by GIUBOSS. this performance will show you where exactly problem start. Fusing or Transfer Belt. Same time pls PM counter on PCDU K. PM count for PCDU K 60K.

Suspect on charging goes up when choose print on Thick 3.
PCDU K
Tranfer Belt

Thanks.

I should have included the fact that I had already eliminated the fuser as the cause.
It turned out to be the K-PCDU causing the issue.
While I did say that I had replaced the pcu not so long ago, it was a used unit that I had installed, and that I had recorded as very lightly used.
Maybe it had more usage on it than I thought, or it might just fall under the heading of "s**t happens"
Whatever the case, it was a bit of an unusual issue, that didn't even show up on regular printing, because the normal printouts were fine.

Thanks!

[mga]

If only pcu fitted remember to setup sp 3902-009. If complete pcdu fitted if new setup done automatically.