nozzle check pattern

My Epson XP-342 is not printing correctly since a couple of weeks ago. Whenever I perform a nozzle check and print a test page, the color segments are perfectly fine but the black are always missing the exact same segments. In fact, if I print over the same printed test again, the black missing...

The printer has less than 500 prints, so I presume there's still much life left in this machine. I wanted to do some preemptive maintenance. The other day, using Windex (no ammonia), I cleaned the purge pads and wiper. Lots of black ink came off on those Q-tips. Nozzle check pattern shows...

Greetings! I have a epson wf1100 that will not print good nozzle checks. It is only black that is giving me trouble. I am using sublimation inks from cobrainks with refillable carts. I have used piezo flush as well as the folded napkin with windex method with no luck. Please see the attached...

My nozzle check printout shows a stubborn problem with MBK despite a lot cleaning, cartridge changing, etc. The best I've managed is the partial printout. The blank one is the most recent. In between, however, I was able to isolate the MBK cartridge and print from it nearly perfectly. I'm not...