Note of the capacitor across the base and emitter of the transistor, it is 100nF (0.1uF)

here's the original schematic diagram for reference: https://im.ge/i/image.UO5q0

That's the pull-up resistor in the Pi - I don't think I can change that

@swimclips if there's potentional corrosion in the cables, you may try to decrease the value of this resistor from 1.5k ohms to 500ohms

I think it is currently 100uF in the circuit I have implemented. It seems to work perfectly - except it didn't at that one particular meet where I think they had a problem with the cables

Oh i think overlooked the original value of the capacitor, I thought it was 100uF. where it should be 100nF

That capacitor being 100uF, you need to press the button for like 5-10 seconds for you to achieve the rising 3.3v on the RPI side.

So try 500pf, if that would make everything fast.

@swimclips Nope, that capacitor has huge value thus when you push the button, that capacitor still has charge making the transistor in ON state instead of OFF.

I suggest TRY smaller value ceramic capacitor like 500pF.

That is supposed to be a debounce filter

@vasy_skral this capacitor causing somewhat weird behaviour here.

R4, this is the added resistance due to corrosion/rust.

From the EE at Colorado Time Systems who drew the original circuit sketch: "The two grounds of the timer and your device are not the same. I sloppily drew it that way in my original sketch. In your simulation the simulator connects them implicitly.

The resistor across the start system is actually not there. Corrosion resistance would be additional resistance from the start pins to your diode bridge inputs. Then you can simulate their values until your pulse disappears."