I narrowed down to these two transistor because i disconnected r182 that is a socketed 8 dip short resistor like this one
https://www.eevblog.com/forum/metrology/misterious-resistor-network-of-shorts-in-keithley-195-input-multiplexer/ and measured the voltage at each pin with the instrument on and only pin 1 measured 85 mv while all the others are 0.1mv , 0.2mv or just 0mv.
Those 85mv come back at r209 at both sides and disappears but not completely ( i measure around 0.4mv) only with the 20v range because in this range k103 closes
Also now the meter with only pin 3, 4 and 5 connected together (so with only the precharge amplifier, the 2v and the 200mv ranges and the output fet connected) measure almost a stable zero with shorted input on both ranges so those input are good.
I have also tried with all the other ranges, one by one and only pin 1 is not zero and drifty
I measured r181 and r183 and i have no leaking here (i have the same 0.0mv , 0.1mv).
So i ruled out q124
It must be q122 because i have a positive voltage leak and only this fet is connected to a positive rail while the other one (q123) is on the negative rail
I have also tried to put my hand on both jfet but no changes are measurable
Maybe i can use q142 or q143 because they are unused (i have no current or ac option)