jerky execution of the control program.

Explain why MK3 / 4 + planets TNG jerky? The machine should work with a constant speed of 5000mm / min. The control program was made for laser engraving.

https://www.youtube.com/watch?v=fR0iOpk0k9o

I am using the MK3/4 with the old USBCNC soft/firmware (not TNG). But I have experience similar jerkiness, slowness and sometimes lost steps when activating the path blend option. It may have to do with a combination of other settings but I could never figure that out. When "path blend" was deactivated, the problems went away.
So, I am not sure if that may also apply to the TNG software but it is something you could try.

It is not possible to compare old CNCUSB software with TNG. TNG uses much more sophisticated algorithms and works totally different.

Regarding jerky execution in video - what you see are not really jerks. G-code is made incorrectly. One line is G0 next line is G1 and then G0 again. When you do this on short segments machine will accelerate to G0 then decelerate to G1 and then accelerate again... This, combined with very fast acceleration on X axis (1000 mm/s2) will result in jerk like motion. Simple fix is to change all G0 to G1.

during these jerks, the speed drops below G0 and below G1, actually up to 300mm / min.

Although it should not fall below G0 and G1

In order for this to work correctly you need to use G-code correctly. G0 should only be used between cuts. On some machines this is not even coordinated move.
G0 and G1 are treated differently by planer. Before G0 segment speed starts from zero to achieve exactness needed by G0. In your case you use G0 where you should use G1.

Then another question is why MK3 / 4 loses touch with the computer? Prior to this, there was a MK1 board and no problems were found using the same computer and the same USB cable.

This happens due to EMI. We recommend using double shielded USB cable, shielded cables for your wiring(spindle, motors, limits), and use line filter with your VFD.
See VFD user manual for appropriate type.

Also, use external power supply for controller.

unfortunately loses touch even with the FVD turned off. The controller is extremely unstable compared to the old version.

And after losing the connection, the program resets all the offset values, this is inconvenient, it is impossible to start from the right place.

I catch myself thinking that the Chinese clone MK1 with aliexpress works better than the original. )

Are you kidding me??? Should I use shielded wires to stepper motors? Maybe your controller is ****?

absolutely all other controllers normally work with ordinary wires.

I have no idea how your controller will work with plasma, although you advertise it. He even idling, without a spindle, loses touch !!! what is it???

Of course you need to use shielded (or at least twisted pair) cables for motors.
Even more important for limit switches. And because those wires are usually thin and long then voltage drop is so significant that operating them on higher voltage via optocouplers is recommended.
EMI filter before VFD is also standard requirement of every electronic box. Not to mention ferrite beads on cables.

It is not controllers fault that you have interference that cause problems. When wiring is done correctly then controller can work flawlessly in extreme EMI polluted environment such as plasma and EDM machines.

You don't need to be rude or insulting if you lack experience or knowledge. We are here to help and not to argue.

Here are some random links about this topic from first page of google search:
https://www.cnczone.com/forums/gener...er-motors.html
https://www.machsupport.com/forum/in...?topic=22812.0
https://buildyourcnc.com/FAQ/901
https://reprap.org/forum/read.php?1,363870

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