Bed Thermistor not functioning  

Bed Thermistor not functioning

I have prusa i3 mk2/s.
So, last night, I noticed that when i was printing, the bed temperature kept changing from 60C (which i wanted) to 26C for no reason. This caused the print to fall off the bed in the middle of print. After that, When I tried again, the bed heated up with no issues.

NEXT DAY
I try to heat up the bed to 60C. No matter how much I heat it, the LCD tells me that the bed temp has not changed, even though It did heat up. Then, it tells me the bed preheat failed.
Later, I do the selftest, and it tells me that the bed thermometer does not work.
In response to this, I looked at all the help guides. I checked the connections on the miniRAMBO, and the tape on the bottom of the heatbed.

The bed thermistor still does not work. 😳 😡
Basically, my bed can heat up, but when it does, the thermostat does not notice any temperature change. I have looked at all the connections, and there is no problem.

Does anybody know what the issue is, and how I can fix it?

Thanks.