Could you please describe the problem in more detail? If you hold the trigger pressed, it stops welding by itself and then restarts? This happens once, or repeatedly ( even with trigger held firmly on ) ? What is the time interval between stop & start, is it always the same time?
If you release the trigger to stop welding, the relay can still be heard clicking? The relay on the PCB, or the large contactor, or both? With that clicking, does the wirefeed motor run ? Does the gas valve open & close?
It sounds like there is a loose connection somewhere, or an intermittent power supply to the logic on the control board. Does the "relay clicking" happen if you remove the Eurotorch? Check for loose wires and plugs around the control PCB. There may be poor connections ( "dry" solder joints ) on the PCB.
Do you get the effect if you do not actually weld ? Turn off the gas bottle tap, slacken the wirefeed pressure roller, then press the torch trigger.
Does the wirefeed motor run smoothly, does the gas valve stay open, do you have a steady voltage about 15 to 25 v DC on the torch tip ( to the "earth" clamp ), or do you get that "relay clicking" situation ? I'm trying to determine whether the welding process, striking an arc, is causing a voltage to drop away and lose control of the relay.
It would be helpful if you could answer the questions and confirm the actions in my post number 4 above.