Can you unplug either of the thermistors and have the board continue to report a temperature for the now-unplugged thermistor?
What I'm thinking is that somehow that the input is bridged. Doesn't make much sense but worth a shot in troubleshooting.
I looked over your config, and don't see anything wrong with it apart from the heaters not conforming with the standard H0 being the bed (I'm sure your slicer will need to be informed about that). Also your temps would be wrong (since you have a top temp of 280 for your bed, and 120 for your extruder).
From your config it appears like you're not using any overrides. Is this issue present from the moment you power on the board? It is possible to have other gcode elsewhere, like in homeall.g for instance if you were really crazy.
My bog standard configuration from a printer I setup the other day looks as follows:
M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin bedtemp
M950 H0 C"bed" T0 ; create bed heater output on bed and map it to sensor 0
M307 H0 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit
M140 H0 ; map heated bed to heater 0
M143 H0 S120 ; set temperature limit for heater 0 to 120C
M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.060000e-8; configure sensor 1 as thermistor on pin e0temp
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit