Help! Why are my prints failing?

[thalassa 9]

I'm so frustrated with my UM3+ today! Printer worked fine yesterday for a 7.5 hour print in UM nylon. I tried the same print 3 times today in the same material, but at "fine" quality setting. All three failed at the beginning with the filament failing to stick to the plate. Before the third attempt I cleaned the plate and put on a new layer of glue. I also did an active leveling of the plate. I thought maybe nozzle 1 was getting clogged, so I put in a new AA print head and loaded UM PLA to calibrate the new head (1). The XY calibration has now failed three times. The PVA isn't sticking to the plate. I unloaded and reloaded the PVA to be sure there weren't issues with the feeder or the nozzle. Seemed fine.

Here are photos of the last XY calibration fail. It looks to me like the z-offset for the BB head is off - it's really dragging through the PLA part of the calibration print. What do you see? Any advice? Something else to try?

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[meduza 191]

Just as a way of finding if the Z offset is the problem i would turn off active bed leveling (set it to "Never" in the menu), then do a manual bed leveling and then the manual Z offset calibration, and then try again.

[tomnagel 126]

I agree that the z-offset of the BB core seems off.

Are you working with the latest (stable) firmware?