This appears to be a conflict with the Nvidia driver (at least for me).
I've tried:
nvidia-378 (open source)
nvidia-370 (open source)
nvidia-375 (proprietary)
All three give the exact same results as above on both 2.4 and 5 Ghz. Switching to the intel graphics driver completely clears this up. It's not a great work around for me as the Intel in the XPS-15 (9550) chokes on an external 4k display with chrome. But it's functional when I need to switch to wifi (which I'm generally not connected to an external display with)
This appears to be a conflict with the Nvidia driver (at least for me).
I've tried:
nvidia-378 (open source)
nvidia-370 (open source)
nvidia-375 (proprietary)
All three give the exact same results as above on both 2.4 and 5 Ghz. Switching to the intel graphics driver completely clears this up. It's not a great work around for me as the Intel in the XPS-15 (9550) chokes on an external 4k display with chrome. But it's functional when I need to switch to wifi (which I'm generally not connected to an external display with)