Skipped layers

[printbus]

Some thoughts...

To eliminate one possible issue, try a print without heating the bed. I realize you have an aluminum heatbed and it might make a difference, but multiple people have demonstrated print artifacts being caused by flexing of the bed heater as it cycles on and off using the normal Marlin bang-bang heater control loop. Migrating to SSR and PWM control of the bed heater is the solution for those artifacts.

What are you using for a filament spool mount? The filament spool needs to unwind very smoothly. If it doesn't (like if you are using the MakerFarm scheme where the filament spool sits on a fixed bar), the filament might be tugging on the extruder until the spool springs free and rotates a bit to relieve the tension in the filament. IMO, the extruder mount on these printers isn't rigid enough to not be displaced by this tugging. Is your hot end a snug fit in the extruder body? A loose fitting hot end would make this worse. Many people have added a thin spacer above the hot end to provide a more solid fit.

FWIW, I never had much luck with the z-hop. The MakerFarm printers can't move Z very fast due to use of the M5 rods, and my attempts at z-hop led to artifacts being caused by the hot nozzle sitting too long in the same place as it slowly rose up/down, and then there's also oozing from the nozzle. EDIT: My best results were obtained by testing to determine just how fast I could accelerate and then move the Z-axis and adjusting Marlin default settings accordingly.