Color prints have two strips of toner that will rub off.

run gradation test, ensure fuser is at correct temp via media thick 1 thick 2 etc paper

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

most likely the OPC (drum) or sometimes called "image drum or transfer belt located in the top draw. this is a consumable that needs replacing after it's life cycle is over. sometimes it will go below or over the life cycle, it all depends on many variables.

I would take out all the consumables, toner, belt and so on and use a dry cloth and small vacuum to clean the inside of the printer, then test it again, but when you have streaks it is usually the transfer belt. other possibilities is the scanner/laser window inside, sometimes it gets toner on the glass.

but step 1 is the Transfer Belt/Drum

hope this helps

clean the laser glass or replace the image unit for the color with the blank strip

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

Not sure if this is what you mean but it is normal for this machine to leave a faint residual image particularly noticeable on heavy weight glossy stock with high toner coverage. I found that it shows up on black the most. I reduced this by rubbing with a soft cloth after printing. You will also notice that the image becomes less noticeable after the oil evaporates. There really isn't a fix for this, it is the nature of the machine. Hope this helps.

adjust your thickness guage as card stock is 3 or 4 times thicker than a 20lb plain paper stock. Here is link to a helpful media guide for HP printers.

http://bizsupport2.austin.hp.com/bc/docs/support/SupportManual/bpl05339/bpl05339.pdf

Hi manitou344:
Here is some info that might help you.

Table 1-8. Tray 1 paper sizes1
Media Dimensions Weight or thickness Capacity
Minimum size paper 76 by 127 mm
(3 by 5 in)
60 to 163 g/m2
(16 to 43 lb bond)
100 sheets
(75 g/m2; 20 lb bond)
Maximum size paper 216 by 356 mm
(8.5 by 14 in)
60 to 163 g/m2
(16 to 43 lb bond)
100 sheets
(75 g/m2; 20 lb bond)
Minimum size glossy
paper
76 by 127 mm
(3 by 5 in)
75 to 120 g/m2
(20 to 32 lb bond)
Maximum stack
height: 12 mm (0.47 in)
Maximum size glossy
paper
216 by 356 mm
(8.5 by 14 in)
75 to 120 g/m2
(20 to 32 lb bond)
Maximum stack
height: 12 mm (0.47 in)
Minimum size
transparencies2
76 by 127 mm
(3 by 5 in)
0.12 to 0.13 mm thick
(4.7 to 5 mils thick)
50 sheets
Maximum size
transparencies2
216 by 356 mm
(8.5 by 14 in)
0.12 to 0.13 mm thick
(4.7 to 5 mils thick)
50 sheets
Minimum size
envelopes
76 by 127 mm
(3 by 5 in)
60 to 90 g/m2
(16 to 24 lb bond)
10 sheets
Maximum size
envelopes
216 by 356 mm
(8.5 by 14 in)
60 to 90 g/m2
(16 to 24 lb bond)
10 sheets
Minimum size label 76 by 127 mm
(3 by 5 in)
75 to 163 g/m2
(20 to 43 lb bond)
50 sheets
Maximum size label 216 by 356 mm
(8.5 by 14 in)
75 to 163 g/m2
(20 to 43 lb bond)
50 sheets
Minimum size
cardstock
76 by 127 mm
(3 by 5 in)
135 to 216 g/m2
(43 to 43 lb bond)
50 sheets
Maximum size
cardstock
216 by 356 mm
(8.5 by 14 in)
135 to 216 g/m2
(43 to 43 lb bond)
50 sheets
This printer can
detect transparencies that were not designed for use with HP Color LaserJet printers.

Most likely you may of had a toner spill awhile ago and the toner may be biult up with in the paper path and it is draging in it. Also, it may have to do with the drum pick off claw unit. The paper may be rubbing against the unit with thicker paper. I would have your service person clean the whole paper path of lose toner and if they can bring another drum unit to test if the problem is in the drum unit it self. Good Luck

suggestions...
first, make sure all your consumables are in good condition, run a configeration page and check the percentages....toners should be 10% or more.
drume should be 50% or more(depends on what weight stock u been running), but run the ID check print, to see drum results.
The transfer belt should be above 20%..
This will ensure your machine can deliver.
next, make sure you have the correct paper weight setting( both in front panel(web browser) and (application drivers) for the stock. If you have setting gtoo high, then over toning will occur.
also, stock must be suitable for laser printing, offset, or cheap paper will drive you nuts....
good luck

You must pull 2 sided glossy from the stack bypass and set on color paper.

it is a fact of digital print that toner scatter will apear ever so slightly. But it is noticable much more on glossy stock, as there is a high reflectivity, and no micro valleys in surface texture to loose it in..having said that...glossy stock is very difficult to print on with the Ilumina..even on label setting/ auto select for weight and Media switch on(this is the best I have been able to achieve)