HP Latex 115 - Issues with black print / white spots

We are having image quality issues when printing black on our HP Latex 115 printer. The substrate we are using in this example is ORAJET 3165, white gloss. It uses the HP certified profile from the online substrate library, and has been calibrated (under image quality maintenance). The original file uses CMYK black with 50/40/40/100 to achieve a rich black colour. The CMYK black appears brown and does not print correctly. We have printed this colour on other machines without issues. Does anyone have experience with printing CMYK black vs. flat black? Other colours on the machine have been fine, but there is a lot of "coalescence" (refer to orange in test print). We have decided to test print with flat black (100% black) which looks much better. Unfortunately there are white spots / flecks on the print. What is causing this issue and how can it be resolved? Thank you in advance.

Sounds like it might be contaminated media. Try wiping an area with alcohol and see if that area has the white spots when printed. If it does then you should demand a replacement roll.

I have this issue on both my 365 and my 335. No matter what materiel I use. Did HP have a batch of bad Optimizer or black in 2020 and 2019? The 365 uses 3 liter boxes.

Hello, i have an hp latex 335 and i have this problem on ORACAL 3641/3651 GLOSSY. On MATT the print is perfect, but on Glossy it is full with white dots. Has anyone discovered the solution? Thx!