Thermostat shows large, sudden jumps in temperature reading (e.g. 20°C to 28°C within minutes) without environmental change

Safety first: The thermostat is low voltage; avoid opening the casing unless you are competent with electronics.

• Relocate if necessary: Move the thermostat away from sources of electrical noise (large motors, inverters) and direct heat.
• Reboot: Power-cycle the thermostat and Heat Hub.
• Monitor with reference thermometer: Place a separate thermometer nearby and log readings over several hours to confirm the issue.
• If jumps persist: The internal sensor or PCB is likely faulty. Replace the thermostat.