I have an Ender 3, I changed its extruder for one metallic one. In my last prints, I am getting issues at the same height. The extruder can't pull the filament in for that z position. I cleaned the Z axis, applied oil, and adjusted the eccentric nuts. I have minor improvements but still have many issues with my prints. I am thinking of changing to double z-axis, but I'd like to use my printer now.
I fixed this issue today on two printers.
One was failing first or second layer, the other after 1/2 an hour or so. After trying everything else I traced the cause to changing the nozzle to cheap steel ones. Changed back to the old brass ones and both printers are working fine.
Unsure what is wrong with the steel nozzles, I bought 10 of them online for peanuts, but happy to be printing again.