Help with homing issue

Have you tried watching the DRO/velocity readouts and backplot in Axis while it is homing? Does Axis show the Z-axis starting and stopping as it travels towards the homing switch, or is it just the motor itself doing the jerky motion? I'd almost suggest you have a hardware or wiring error of some kind from the way the Z axis is moving in that video.

I had weird homing behaviour when I built my first machine that I couldn't get my head around for a while. My axes would jog around fine, but would do odd things when homing, like not backing off a limit switch when tripped or Axis continuing to show movement after the steppers had stopped. It wasn't until after several hours of playing with settings in the INI file that I realised I hadn't powered the breakout board from the external 5V supply

I set stepgen_maxaccel to 8, nothing changed though.

Axis DRO is following stop and go movement of the axis. I can manually enter gcode on each axis and get smooth consistent travel.

I did find that if i keep pressing home button after it errors that after 5 to 10 tries it will eventually click the switch and move to home.

I was asked about the kernal by someone, this is what i found, not sure if it was what was needed
drive.google.com/open?id=10qYVz1ET4bnv7KjTFOoc2763QwO72sfvOA

I am not even sure what a servo thread is or how to check it.