[gnea/grbl-Mega Issue#116] Spurious error 33 with $101 change

If I set $101=64 then this file consistently fails with error 33 around the second to last probe, but it consistently passes if I set $101=128. To simulate the probe I use a jumper from ground to pin A5 and pull it out briefly while it’s probing. Error doesn’t occur if I let the g38.3 time out. My machine is actually ~16.7pulses/mm, but I narrowed it down to 64/128 as the threshold where it starts passing.

Here’s the relevant log snippet from bCNC:
“
...
G38.3Z113.81F0.0001
[PRB:35.813,1.078,4.063:1]
ok
G01Z3.81F4572
ok
G04P0.4
ok
G01Z1.524F4572
ok
G03X35.814Y1.0858I0J1.3907F5080
error:33
“
G-code. (This bug also occurs on a different G-code file)
g-code.zip

Here’s my setup:

$0=10
$1=25
$2=0
$3=0
$4=0
$5=0
$6=1
$10=1
$11=0.010
$12=0.002
$13=0
$20=0
$21=0
$22=0
$23=0
$24=25.000
$25=500.000
$26=250
$27=1.000
$30=1000
$31=0
$32=0
$100=64.000
$101=128.000
$102=128.000
$110=5000.000
$111=5000.000
$112=1000.000
$120=2000.000
$121=2000.000
$122=2000.000
$130=200.000
$131=200.000
$132=200.000