Lead-in going beyond path

Not sure where the problem is.
At the beggining of a cut, I did a Sheetcam arc lead in of 3mm. Looks good at sheetcam and QtplasmaC visualization. But I am getting this results:

 

I have done some testing, with/without THC, turn down g64 p to 0.05,  slower feed rate,  arc ok off, none seems to help.

My machine uses GT-2 10mm belts, it might be related to backlash (I can see a wiggle after a 90º turn).

How would you investigate such an issue ?  
Thanks

Preamble looks like this:



I am cutting at 2400mm/s, but have tested with 60% without any visible difference.
 

Sharp corners wobbling is for sure due to flex/slop/loose stuff, always mechanical on stepper systems.
You can try lowering acceleration, it helps a lot but only to a certain point.
Using GT2 belt on a 20 KG gantry is manageable and works OK, but on a 70 KG gantry nothing helps short of slowing it to a crawl.

Yes, I will check for mechanical issues. And try to lower accel. Thanks.

I think my gantry is near 18kg, never weighted it.

Have seen this topic ( forum.linuxcnc.org/38-general-linuxcnc-q...ad-in-on-inside-cuts ) and additional info follows:

PARAMETERS > THC > SPEED: 10%
PARAMETERS > THC > VAD THRESHOLD: 90%
PARAMETERS > MATERIAL > PAUSE AT THE END: 0
PARAMETERS > MATERIAL > CUT HEIGHT: 1.5mm
PARAMETERS > MATERIAL > CUT FEED RATE: 2400mm/s

I have tested and the "divot" happens at the start, not at the end of cut (when there is less material around the plasma).

I have set negative overcut of 1.4mm (on Sheetcam) and it didn't help.

EDIT:    I have MAIN > CONTROL > VELOCITY ANTI-DIVE checked and it lights several times when cutting  (not sure if it has any relation to the problem

Would this have anything to do with FERROR and MIN_FERROR ?

See above, if stepper system = mechanical issues.
From the cuts i am fairly certain it is a stepper system.