No, because the spring is where the centrifugal device is.
When you open the PV with the linkage engaged, it can happen that the steel ball go out and than you have to open the clutch housing and repair this.
In my opinion there is a carb problem and no PV.
You don't have to buy a YZ piston, woessner, vertex, wiseco, etc have GasGas pistons. If you don't have a good dealer in Sweden, send mr. Dubronner a email, he is the former German GasGas distributer and has everything on stock
In Europe a 125 piston cost about 100,-€ no matter which Brand. Before you are looking for a YZ piston, check which geometry you have, the flat top or the dome.
Have you checked all of the electrical connections for tightness and cleanliness?
I had a similar problem with my EC125 and it was a loose wire connection to the coil. Squashed the connection so it was tight and never had an issue again.
Wonder if a connection was wiggled enough to temporarily fix the issue when you changed the carbs around.
Yesterday i let my friend ride it to hear his opinion. First he said "it runs like any 125" then i told him to start up his ktm 125 to compare. Then he said "aaaha! Now I understand what you mean, strange"
Maybe try to swap the cdi ignition boxes between the bikes and see if the 125 cdi is bad. The timing curves are different but it should let you know if one is bad. I walls agree that you should check all of the ground and electrical connections.