Wide z banding on larger prints only?

[Savvysawce 0]

I am running out of ideas on how to adjust these lines!

 

Finally got around to trying a helmet (Moon Knight) print and noticed these bands or ripples, so I stopped before the dome finished up top.

After doing some digging, it seems to be from possible z axis wobble? Most references I've seen due to this look a lot smaller than what I'm experiencing, as these ripples seem wide or tall, and slightly angled.

 

I changed out the rod, even though mine looked pretty straight - no change

changed out the brass nut to an anti backlash nut - no change

Squared up the z stepper motor to the aluminum frame, and changed out the mount - no change

Made sure there was a tiny bit of separation between the z rod and the motor in the coupler - no change

Tried adjusting jerk and acceleration settings, and printing slower (40 mm/s) - no change

 

Printer and settings:

Longer LK5 Pro

Cura 4.8.0

Filament: SUNLU PLA at 205/60

Nozzle: 0.4

Layer height: 0.20

Speed: 50mm/s

Wall line count: 2

Wall Thickness: 0.8mm

Infill Density: 20%

Retraction distance: 5mm

Retraction speed: 50 mm/s

 

 

The part that I can't wrap my head around is that it's really only happening on one side as well (the side the gantry is parallel to, or the front of the bed). Not only is it on one side, it also doesn't seem to appear at all on smaller prints. I'm attaching pieces of an E-11 blaster that REALLY show the lines. I printed one at 50% and the wobble is basically non existent.

 

My last hope is maybe re adjusting the gantry itself. I did notice a wheel on both sides spinning almost freely while the others have a decent grip, so this will be the next thing I try adjusting.

 

Any help or guidance is welcome!