@fcwilt Ah, the S flag was 60 and not 70 (307 D was 70).
M303 H0 P1 S60 with the 307 (to increase dead-time) first gets:
Warning: M307: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 365C
Auto tuning heater 0 using target temperature 60.0°C and PWM 1.00 - do not leave printer unattended
2021-07-29 18:54:05 M307 H0 B0 D70 S1.00 V0
2021-07-29 18:54:35 M303 H0 P1 S60
2021-07-29 18:54:40 Auto tune starting phase 1, heater on
2021-07-29 18:57:50 Auto tune cancelled because temperature is not increasing
Which was weird, not it won't power on at all.... and the last times were inconsistence (could power on manually but during cool down could not turn on again)...
20210729_200326.jpg
20210729_200333.jpg
Removed my temp fuse (130 C) and found that it looked burnt.
Probably wired it wrong since I haven't even attached it to the heat-bed yet, just connected it to the power, it was just hanging for now. So I guess I need on that can take more Amps.
With it removed it looks much better:
2021-07-29 20:01:10 M303 H0 P1 S60
Auto tuning heater 0 using target temperature 60.0°C and PWM 1.00 - do not leave printer unattended
2021-07-29 20:01:16 Auto tune starting phase 1, heater on
2021-07-29 20:02:14 Auto tune starting phase 3, heating system settling
temp2.png
Update
It was the Thermal Fuse that was not rated for the amperage and slowly started to mess with the heating instead of just cutting it of.