Hrm, I had similar issues on my Artillery X2 before.
Here’s what I went through:
Replaced the nozzle
Replaced the thermistor
Replaced the heating block
Replaced the main PCB
Replaced the heatbreak
Finally, I gave up, and took out the thermistor again thinking maybe I broke it. There’s a small PCB connected to it, that sits on the side of the hot end assembly. I contacted Artillery about a potentially faulty hot end PCB, they sent me a replacement. It did not help. Desperate, I also replaced the thermistor with the replacement one that was part of their repair kit. And that worked. I think the faulty PCB broke the first replacement thermistor or something…