Thank you, you have forced me to remember the golden rule of investigateing. Start simple and at the beginning. A wobbel is the rocking mothion resulting when two flat serfaces come in contact with each other and are not actually flat. Either the USB has a crown on it and is not flat or the flat of the blade of the chisel has the crown. It is the only way I can think of that there can be a wobbel, in this case. It looks like a factory serface in both cases so I will start with the blade and try and flaten the chisel. Without two flat serfaces comming together it would be imopssable to grind a flat cutting serface. By the way the stone has been trued multiple times so unless the trueing tool is not working correct the stone is true and it is going to be hard to check more than every few seconds. Also I understand you are covering all the bases.