Switching off the HP inks should be a separate subject here I think. The HP ink should still cure and perform as expected.
Adhesion, elongation, and longevity can be symptoms of bad ink batches, but bad ink is very uncommon so I wouldn't pick it as first assumption. Additionally, if the ink was at fault it would likely be "dry" to the touch but failing to adhere. Since you say it's still tacky, it sounds like a curing issue for sure.
You said it's a "new box", but to some people that means a few weeks old. Make sure you shake your ink boxes daily before running so they don't separate. If you haven't been doing that and the ink is over 30 days old, then shake it up good and purge it 5 times to flush fresh stuff in.
Easier medias like vinyl rolls may be scraping by under-cured without you noticing since they behave so much better. The issue may be really showing itself on more difficult media's like coro.
1. Most common curing issue on those models is improper shutter alignment. Validate your shutters are pointing full down and that you're running BOTH shutters to cure for that media. Trailing shutter cure will not be enough for coro. Shutter alignment can be found in the individual calibrations menu I believe (working from memory here).
1a. When checking shutters, those often go completely out of wack due to some software or hardware malfunction. If they clipped or snagged internally they can be completely closed when curing. Those shutters also DO break completely and fail to rotate or can be stuck on an edge internally.
2. Change both bulbs anyway. Just because they are within lifespan doesn't mean you didn't get a dud. I have seen plenty of bulbs last ages past EOL date and equally as many die in half the span. Performance of UV bulbs is very inconsistent.
3. Pro-tip for digital coroplast often untold: Always run less ink and more incremental curing passes. In very short, adhesion-challenged substrates cannot handle the ink loads of better substrates. In the FB printer's case, always run 300dpi at max passes, Outdoor plus. This gives you immediately lower ink densities than your 600 calibration while giving you more curing passes. Note: Blasting the ink with more UV to cure is not the same as incremental curing. More passes cured in succession creates a completely different surface tension and adhesion profile than less passes at higher UV exposure. Also note: An ICC set for 600dpi and 240+ ink limit will always have adhesion problems on that printer on low surface energy substrates like coro.
4. Pro-tip 2: You can run that press all day with your 300dpi profile calibrated on vinyl. But if you run a lot of coro and want the best results for finishing, cutting, and general adhesion, then make "Low Surface Energy" calibration with a total ink limit at like 220 (or your desired limit for your applications and color needs). Will work wonders.
