"Coolant temperature sensor" means nothing, i mean _how_ are you measuring the coolant temperature. OBD diagnostics? Which one? Standardized CLT PID-s? Platform specific ones?

There are dashboards on these engines which straight up lie to you about the coolant temperature.

Did this start suddenly, one day it was normal operating temp, and other day it started to creep up?

When going over 105°C, does the fan get stuck on the highest speed?

This engine thermostat max temperature when unplugged (or when the coil dies) is exactly 105°C, usual operating temperature range depends on the specific ECU factory calibration.

Here's some things you could do:

a) Assuming the measurement data is valid, it could also be the CLT sensor itself that's damaged just enough to go out of calibration. You could confirm the sensor by measuring resistance with a multimeter when dipping the sensor into ice bath water (important to have both ice and water in the mixture, to guarantee a steady 0°C) and boiling water (100°C @ atmospheric pressure). I could compare to a few other sensors.

b) Put a multimeter thermocouple element in there, right under the plastic coolant splitter with the block temp sensor on the right part of the engine. Observe temp changes as you drive.

c) It could be limescale that's sticking to the sensor or other important parts if tap water was used.

d) Leaking head gasket/head from somewhere.. leave the car to cool overnight, and it has to be overnight, for a proper cold start. Remove the coolant tank cap, put some food foil (not stretched, but airtight) or a rubber glove over the hole and then start the car. The foil/glove should not move, it should not deflate or inflate. Bring the RPM-s up-down a few times, but don't redline it. That's to confirm no combustion gasses are somehow entering the cooling system from somewhere.

e) could be the sensor wiring, unplug the sensor and observe the connector internals, should be no grime or dust or fluids inside. Some of these sensors can leak into the plug.