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Not odd at all, it is a feature (in the original firmware) to prevent grinding the filament, if the hot end cannot extrude.

I think that threshold is 90 Tdegc, so somewhere (in the firmware) you can overwrite this.

My build does not use the latest version, that is correct, modification done to this firmware is described in the Google docs...

Do take note, the Arduino board has a 12V to 5V down regulator (a linear regulator), this tends to heat up, my documentation detail this, and how to address it.