Thermistor issue or ???

[zemlin]

I know the wire harness is a possibility for a flaky connection, but I don't think my #2 harness has enough miles on it to have an issue. Could be wrong.
Going to let the print keep going to see what happens.

[ednisley]

wire harness is a possibility for a flaky connection

I'll vote for a going-bad thermistor, as I usually do. [grin]

On the five-minute-per-division timescale, the variations look entirely too slow, small, and regular to be caused by wire flexing.

Perhaps the thermistor pellet expands & contracts due to the hot end's slight temperature variations, causing similarly small resistance variations in the contact wire joints?

It'll take long enough for a catastrophic failure to let you order a new thermistor, anyway.

[zemlin]

It'll take long enough for a catastrophic failure to let you order a new thermistor, anyway.

Thanks. I have a couple in the parts box - I'll swap it out when this print finishes.