[Squid]

I have a little router Geko 540 controller, Mach3 Mill... Its a twin motor Y axis (slaved Y on A) single X and Z axis.

Ive tried to Interpolate 9mm holes at 3.5cm grid pattern to take some inserts to make a bolt down table top. with a 1/4" Router bit. everything seemed fine.

Lets say i have A-K along the bottom so that would be X axis. and 1-20 on the Y axis.
All 20mm deep.

One CNC made the tool path and the first 2 lines seemed fine.
so that would be A1-K2 all drilled/milled fine.
Today i started to fill in the rest of the board and i have hit trouble.
The X axis all look inline, and initial depth all looks fine too, its the Y axis is all over the place.

For example.
Looking at the CAD everthing is fine, Looking at the Screen in Mach3 and rotating the image it all looks inline. the rows all line up from left to right, Up and down, and the 45 deg angle all lines up.

the reality of the cuts is that the rows look fine looking up the machine but cross ways thay are up to 1.5mm out and some are slightly oval in shape. Max 1mm.

not all are out of alignment, but there seems a higher chance of the ones chosen in a diagonal are more likely to be out that the ones in a more systematic approach... for example.
first cut to last cut in sequence.
A1, A2, A3, A4, B5, C6, C7,C8, D9, E10.

so its more likely, but not exactly, that the B5 and C6 and D9 will be out of line to the rest.

Any clues what to look at?

[Squid]

i suppose there could be more info involved here. The feed rate of the first op were 190 on the plunge, and 380 on the feed.
the feed rate on the second op the ones that has given me trouble is 200 and 400. but even if i ghost cut the program for a second time it seems to still follow the messed up route without cutting "better" positions. It repeats the problem so im not sure its skipping a step, or slipping somehow...