I found my problem, looks like I had a bad bed transform loaded. Apologies.

On my printer [c]G30[/c] seems to make the print head go back up 20mm after the probe.
Not only that but it sets the z=0 value way too high up.
[c]G30 S-1[/c] doesn't do that and the measured z seems fine.

I'm about to revert to 1.21RC1 which I was using before and wasn't doing this. Can you think of a reason for this to happen?

I'm going to mark this as solved (i looked around but couldn't find a way to edit the topic).

I got an answer about the bltouch repeatability. I'm happy to use P9 and Axx in the my probe definition.

I'll address my G30 problem in another thread.

good job man!

@Phaedrux:

When it's probing does it look like it's skipping some points? Or like the it starts to probe but triggers immediately and moves on?

I've been having similar issues with my BLTouch. Thread here:
https://www.duet3d.com/forum/thread.php?pid=43389

Video of failed probe point.
http://www.sensibleserver.com/probespike.mp4

Oh wow, no my problem is different. Visually it looks like it probed fine, it's just the value that is wrong.

Hum, I just upgraded to 1.21 from github releases and I'm having a problem with G30 now.

I'm using
[c]M558 P9 H5 F100 T6000[/c]
and
[c]G31 X48 Y15 Z1.6 P25[/c]

When I run G30, it probes, but then seems to go back up about 20mm yet webui says Z=0.
So when I add A3, it does the first probe, but on the second attempt it doesn't reach the bed.
[c]Error: Z probe was not triggered during probe move[/c]

My deploy and retract scripts have nothing special in them:
[c]M280 P3 S10 I1
M280 P3 S90 I1[/c]

I wonder what could be wrong.

Thank you! I will upgrade from 1.21RC1 and test out the A(nn) parameter.

Hello, I sometimes get some bad z values probed by my bltouch.

This is a heighmap where this happened

[c]
RepRapFirmware height map file v2 generated at 2018-02-24 12:33, mean error -0.496, deviation 1.159
xmin,xmax,ymin,ymax,radius,xspacing,yspacing,xnum,ynum
5.00,245.00,20.00,225.00,-1.00,40.00,40.00,7,6
-5.662, -5.662, -0.388, -0.395, -0.385, -0.457, -0.452
-0.308, -0.308, -0.308, -0.278, -0.308, -0.263, -0.293
-0.308, -0.308, -0.183, -0.138, -0.178, -0.180, -0.295
-0.175, -0.175, -0.175, -0.077, -0.130, -0.160, -0.290
-0.175, -0.175, -0.212, -0.115, -0.148, -0.148, -0.190
-0.263, -0.263, -0.263, -0.185, -0.180, -0.155, -0.135
[/c]

The first points are wrong here: There's no way there is 5mm z offset.
I can probe again and eventually will obtain more realistic values, closer to the remainder of the points.

This started happening when I changed print head to test a dual extruder.
Do you guys think my probe is damaged?

Also, this test was done with all heaters and fans off.

On a related note is there a way to make multiple probes of a single point? I would expect this method to eliminate abnormal results and and perform some kind of average.