Clutch pedal

Very strange, never had these problems before

how do old/new slave parts match up ?
Possibly didn't notice boot on old one or it stretched more !
Have you had someone operate clutch so can see the fork moving and return correctly, If fork sticking or slave piston sticking then it will keep pumping further out.
I've had similar when fitting new bits and sometimes things are little different and sometimes I not fully noted original alignments and they same when revert back and check .
does look a lot of distance between slave and fork in pic though, mine sit closer to slave than that.

ill do a full match on the weekend and see if there is anything different, I have done almost everything I can to make sure its bleeding correctly, I feel its got to be something else.

When u dropped the piston of the slave cylinder did you put it back in the right way?

Piston goes in bore seal end in first, can't see you getting that wrong really, end of piston has bore that the push rod sits in, is it fully seated in this !
To me it looks like distance between clutch fork and slave is quite large.
If both slave castings mount giving same base position and piston and rod both very very close then it can only be fork position or slave piston sticking (not returning) and then being pushed out further next time pedal depressed.
Does master stroke range seem right via yoke adjustment. I normally bleed slave unmounted (just my way & not a must) and use a hand clamp hold piston and rod back then bolt slave on and operate pedal to take up slack and position piston.
Does clutch pedal feel normal when depressed, does slave rod and fork arm move back and forth when pedal operated, have seen people hydraulically pump piston out during bleeding so clutch fully disengaged & slave apply pressure on fork even with pedal up as master stroke not full range .
Checking function and parts should conclude something . PITA but excuse for a tinny and few hours in garage over weekend :-)

So I switched the master back to the original today, and the clutch seems a lot better. I don't have a working slave cylinder to compare if they are exact because the piston on the original is seized in there.

So the clutch seems ok, but the piston on the slave sits about 6mm out of the housing when the clutch is pressed to the floor, that doesn't seem normal? Anyone able to check theirs out?

I'm almost tempted to just buy genuine master and slave and quit fucking around with this crap.

That travel range seems off, mine still in the bore when depressed . Do the slave push rods match up in length & countersink in piston same? does slave housing match up in length and mounting position (just measure mounting holes to end of housing piston bore) .
In your previous image gap between slave and fork seems look unusually large so would expect obvious difference in slave measures somewhere if that the cause .
Try soaking old slave in release oil and knock piston inwards after soaked for a day or 2 then try force it out with compressed air or hydraulics . If old cylinder frees off you might rebuild it with new seals or do a trial test as is to see if difference or not . being PITA this :-(

I can confirm the slave push rods match up and there wasn't any noticeable difference in the salve housing. Ill soak the old slave and see if I can get it moving and measure up

Can't really see piston being that much different unless pushrod is fitting deeper in piston thus making it shorter . I've used trw and nippart master and slaves without difference in function. It not unusual find some design/machining difference in after market pistons but what want check is push rod exposed length with pistons level at end of bore stroke, if that same and mounting of slave housing casting equal then travel range got be fork position related, is the fork sat on the ball pivot fully and release bearing properly as either of those can cause fork sit further away from slave assembly .

Brought genuine master and slave, a lot lighter than what I remember though, maybe that's just because of the car I drive around daily, made some adjustment to the master rod and stop bolt, seems really good now, now put all the inlet etc back together

Whats the slave rod throw like now then woody .

its about 2-3mm out of the housing rather than 6-7mm now, looks alot more normal now B.

The master was probably alright but just thought screw it and use genuine.

Bit odd, can only see fluid displacement or fork adjustment being issue as parts measured up. Can't go wrong with oem nissan parts just shame they don't price stuff little better. Least sorted and can move on to all the other shiny bits you bought ...