The temperature sensors are usually NTC thermistors mounted in a housing. NTC (negative temperature coefficient) means that as the thermistor temperature rises, it's electrical resistance drops. The measurements you made need to account for temperature of the sensor, for example is it in your warm hand or outside in the cold.
If you are talking about the air sensor in the air box, it is usually trouble free, unless your friend is in the "pod filter" brigade. Then he needs to mount the air sensor somewhere where it measures only intake air. https://www.v11lemans.com/forums/index.php?/topic/19831-air-temp-mod-for-no-air-box/
Since a thermistor circuit is usually low current to avoid self heating, the circuit is sensitive to extra resistance from a bad connection. Unplugging and replugging connectors can help, especially if you clean and treat the connectors with something like DC4 or DeoxIT.
I bought packs of 20 thermistors from Aliexpress for about $2 a pack. Let me know if you want a selection sent to you, I know I will never use them all. Note that the rating for thermistors is measured at 25 degC.
The illustration below is for the V11 air intake sensor, but the V11 oil temp sensor has the same rating thermistor in a different housing.