My Lenovo X1E regularly burns 20% of its CPU cycles on some high frequency recurring interrupt. I did get pretty far with debugging it, but eventually gave up since I can't justify spending so much time on fixing a 'professional' laptop that I paid top dollar for.
It also has a multi-GPU setup that has never worked reliably under Linux, which is ironic as I opted for Lenovo due to its supposedly good Linux compatibility.
Switching between GPU modes is a hit or mis, waking up from stand-by often results in a blank screen, screen flickering, sporadic high fan speeds, etc. And then there's the coil whine, which seems to be fixed in some BIOS versions, then returns in the next. Supposedly it has something to do with power-saving measures.
Since I owned it there have been at least 20 BIOS version releases for 'improved performance and security', but none seem to actually fix anything. It's such a mess.
/rant