Recently my 2080 Ti start having this fan speed spiking issue, where it goes suddenly extremely high(beyond standard 100% rpm) then falling back to the fan curve speed.
Reading a few cases, most people suggest sending it for RMA on similar cases but after digging a bit more this seems to be due to poor contacts or thermal paste application.
Not wanting to replace this 300A unit, I decided to just swap out the paste. So far it seems to fix the issue and thermal is around 5-12c lower, depending on load.