Now facing the same situation on a X1C printing PCCF at 290 at mid print. When retrying, temp hardly reaches 255, then drops back. I’ve noticed if I use the BStudio “move head” controls, sometimes the temp fluctuates so it could very well be bad connections somewhere… Time to unplug and replug and see if it helps 
I previously used a connector guide which made it easier to plug in the various connectors after swapping the nozzle. After months of occasional nozzle temperature errors (fixed by reseating the connections) I realized that this guide was causing the plugs to come loose. I imagine it’s because it shakes around during printing.
Since I took it out many months ago, the issue hasn’t recurred. I tried warning people with a comment in the model, but it’s buried by the hundreds of glowing reviews. If others are having similar problems, I doubt most would know why, because it tends to take weeks to manifest.
Here’s what the problematic (for me at least) mod looks like:
I’d suggest @BambuLab take a look at their telemetry to see if there’s a correlation between people printing this (and similar models) and people experiencing this error code.