x201(t) thermal throttling issue

I'm having issues with my x201 tablet, the normal x201 runs best as a daily driver. But the tablet always throttles the CPU out if nowhere. They both have the same heat generating top processor, but the normal x201 never throttles. I repasted the unit, tried tpfancontrol but not yet throttlestop to every extend. I am really out of ideas at this point. Nothing worked. The tablet is a nice machine but unusable on 1,17 GHz when it's designed for 2,67. Could it be an issue with the mainboard, the CPU, the fan or the heatsink? Hot air comes out very good, no dust in there. I know the x201 has thermal issues but I can't get over it that the neally identical machines don't share the issue, one gets hot and stays powerfull, one decides to throttle. I'm using windows 10:)