Nevermind, Fixed it - Problem was the order of my commands, I now moved the M140 and M307 to before the M143 definition:
;; thermal -------------------------------------------------
; Sensors --------------------------------------------------
M308 S0 P"bedtemp" Y"thermistor" T100000 B3950 A"Bedmat"; configure sensor 0 as thermistor on pin temp0
M308 S1 P"e0temp" Y"pt1000" A"Hotend" ; configure sensor 1 as thermistor
M308 S2 P"ctemp" Y"thermistor" T100000 B3950 A"Chamber" ;Chamber fan
M308 S3 Y"mcu-temp" A"Board"
M308 S4 P"e1temp" Y"thermistor" T100000 B3950 A"Bedplate"
; Heaters --------------------------------------------------
;Bed
M950 H0 C"bedheat" T4 ; create bed heater output on out0 and map it to sensor 4
M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
M140 H0
;PID Settings
M307 H0 A301.0 C845.3 D1.4 S1.00 V23.6 B0
M307 H1 A482.6 C291.7 D5.5 S1.00 V23.6 B0 ;V6
; Monitors & Limits
M143 H0 P1 T0 A2 S110 C0 ; Regulate (A2) bed heater (H0) to have pad sensor (T0) below 110°C. Use Heater monitor 1 for it
M143 H0 P2 T0 A0 S120 C0 ; Fault (A0) bed heater (H0) if pad sensor (T0) exceeds 120°C. Use Heater monitor 2 for it
M143 H0 P0 S110 ; Set bed heater max temperature to 120°C, use implict monitor 0 which is implicitly configured for heater fault
M143 H1 S400 ; set temperature limit for heater 1 to 275C