Thermal Runaway error

My TAZ5 has the E3D Titan Aero PRO Toolhead. For the past several months, there has been no issues. Recently, there has been an issue with thermodynamic runaways. These problems never occur during the initial part of the print. They almost always occur at least 1 to 4 hours after the print starts. The only recent change I have done was changing the nozzle. I think that either the thermometer on the hot end is damaged or the cooling fan has been set too low. I also have a silicon sock over the hotend, but it worked with it for the past several months. What could be the cause of the problem? Anyone else had this issue?

Changing the nozzle on the hot end may have led to wiring damage on the thermistor. Reach out to the support team at with pictures of the hot end heater block and they’ll be able to point you in the right direction. You’ll be able to test resistances and for continuity of the tool head wiring and harness if you have a multimeter as well.