Same problem, I suspect bad firmware.
A quick interrogation with Throttle Stop to see what's going on shows TPL1 (Power Limit 1) being hit repeatedly, almost to the point of constantly being on.
Scenarios investigated all baselined with SB3 on a Surface Dock 2 with it providing power, running 2 * Dell external monitors over USB 3. Also baselined without the dock and external monitors.
Scenarios that seem to cause this:
- Any VC apps, Teams in particular
- Some CPU intensive games (not so much GPU side of things)
- Standard Aida64 CPU stress test.
Eventually the TPL1 will become a ProcHot as well and the back of the screen feels ready to fry eggs. A reboot results in a shutdown on some occasions and the "im too hot" screen on boot leaving you with a few minutes of waiting for it to cool down.
MS - this is not good... all laptops throttle yes... but pretty much constant TPL1 followed by a runaway thermal spike that nearly cooks the device???