I have seen both happen, print heads and dirt cause drips. If it is the print head it shows up as a more consistent drip singular in colour, more predictable with ink loads per print. If it is hair, lint, gummed up wipers, it can be any colour, and multiple random drops regardless of ink loads per image.
Print head failure is far less present in the Z printers yet there have been some reports already here. Dirt is and has been a concern from the beginning with all inkjet printers , and the Z printer is no different. Whether or not there is more risk on a Z I don't know. Yet I did have a problem with build up that required cleaning. As Ernst said a user control to park the heads to the left to allow full access to the cleaning station would eliminate the archaic way of unplugging the printer when the carriage is in midstream.