What does this problem look like to you?

Have you run out a few more feet of media and tried to print again? What about a different media?

Start with simple solutions before suspecting its the printer.

 

Too much ink + low heat. Try more passes or/and higher heat settings. What you see is ink gathering around dust particles as they are not absorbed by the media quick enough. You can actually see the dust in the middle of the patch.

 

Looks like simple dust to me. Tim's suggestions are sound.

Keeping the shop relative humidity at 40-60% can help keep the dust out of the air too.

For solid colors/heavy ink coverage stuff I do try to run those jobs specifically a bit further into the day's workload so that any dust has already worked it's way out of things.

 

I've never had good luck cleaning material unless it was do-or-die. I just make sure the platen and rollers are relatively clean and then go back into the roll until I reach virgin, never seen air, vinyl and try printing on that. The more you handle stuff the worse it gets generally.

 

The photo was printed using the same media and same settings?

What are you "pre-cleaning" the media with?

The stuff comes off the roll about as "clean" as it will ever be. Any cleaner, wipe, etc.. we apply to it only risks contamination.

 

9 times out of 10 when people post pictures of problems with their prints, too much ink is at least part of the problem... I have posted that so many
times, I'm getting sick of seeing my own posts...

 

"Fisheyes" just like auto paint. Surface is contaminated. Wipe with 90% IPA. Make sure material is dry before printing.

I have some 4mil matte in stock that had did the same thing at the beginning of the roll. Just remembered I had some banner do the same thing. Cured both with an IPA wipe down.

 

It’s simple static dust particles.

 

i used to have this problem on my mimaki, and thought it was contaminated roll, but problem persisted throughout multiple rolls..... but it was actually flecks of debris being kicked-around by the carriage belt during operation, raining-down onto the print.

 

That's a new one. But dust only collects on parts we can see.

 

I had this on my Chinese printer... After i flushed solvent through the head i had some more of them and then the head was clean. Looked like blotches of dried ink particles.

Dust on the vinyl is makes clear spots, what this looks like is blotches of ink.
What inks are you using?