Disco 2 fading brake pedal

Ok got a disco 2 in for welding and other bits n bobs replaced brake lines as they were leaking, new n/s/f calliper as it was shot, new pads all round n rear discs.

Pedal disappears when running hard when not, removed vacuum pipe it's hard.
We have bled the brakes so many times even clamped each line to which it still fades.

Clamped all lines together pedal stays hard yet we still can't find the problem, could this be the servo as I had a similar issue with ml (burst seal on servo behind pedal)