MPCNC Rambo Dual endstop ALARM:8 (Homing fail)

2 year old MPCNC Rambo Dual endstop GRBL on CNCjs. was running beautiful 2 months ago. started it back up, hit the blue homing button and X moved 3mm in positive direction and ALARM:8 (Homing fail). Did status report ? on each of 4 switches X1(<Idle|WPos:3.000,-1.500,0.000,3.000,-1.500|FS:0,0|Pn:YXYH>) Y1=Y gone, X2=X gone, Y2=Y gone. Turned soft limits off and jogged machine, all move correctly. Moved X and X2 to start touching switches and hit homing X keeps going in negative direction skipping belt teeth. have not changed anything sense last run.

$0=10 (Step pulse time, microseconds)
$1=255 (Step idle delay, milliseconds)
$2=0 (Step pulse invert, mask)
$3=21 (Step direction invert, mask)
$4=0 (Invert step enable pin, boolean)
$5=0 (Invert limit pins, boolean)
$6=0 (Invert probe pin, boolean)
$10=16 (Status report options, mask)
$11=0.020 (Junction deviation, millimeters)
$12=0.002 (Arc tolerance, millimeters)
$13=0 (Report in inches, boolean)
$20=1 (Soft limits enable, boolean)
$21=0 (Hard limits enable, boolean)
$22=1 (Homing cycle enable, boolean)
$23=27 (Homing direction invert, mask)
$24=500.000 (Homing locate feed rate, mm/min)
$25=2000.000 (Homing search seek rate, mm/min)
$26=250 (Homing switch debounce delay, milliseconds)
$27=3.000 (Homing switch pull-off distance, millimeters)
$30=1000 (Maximum spindle speed, RPM)
$31=0 (Minimum spindle speed, RPM)
$32=0 (Laser-mode enable, boolean)
$100=100.000 (X-axis travel resolution, step/mm)
$101=100.000 (Y-axis travel resolution, step/mm)
$102=400.000 (Z-axis travel resolution, step/mm)
$110=7200.000 (X-axis maximum rate, mm/min)
$111=7200.000 (Y-axis maximum rate, mm/min)
$112=400.000 (Z-axis maximum rate, mm/min)
$120=400.000 (X-axis acceleration, mm/sec^2)
$121=400.000 (Y-axis acceleration, mm/sec^2)
$122=200.000 (Z-axis acceleration, mm/sec^2)
$130=600.000 (X-axis maximum travel, millimeters)
$131=600.000 (Y-axis maximum travel, millimeters)
$132=120.000 (Z-axis maximum travel, millimeters)

Sounds like the switches are wired wrong. Should be wired normally closed.

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Also, if it actually skipping belt teeth and not just skipping steps (not that easy to tell the diff), then your belts may be too loose. I always make a sharpie mark on my pullies, so I can see visually if Iā€™m dealing with slip vs skip.

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thanks for the help. Set $5=1 and homing works, my concern now is GRBL says i need a pull down resistor, what size and where to put it.

thanks again