Hope C2 - pistons stick out and travel unequally

[thetho]

When refurbing my C2 calipers, I used very decent old and brand-new pistons and seals and screwed them in so that all of them stuck out equally, probably sth around 0.2 mm, trying to make sure not to overtighten them (instructions say 2 Nm, but hard to tell with a pin spanner). The bleeding process seemed to go alright, as far as I can tell - braking feels fine without any noticeable sponginess.

Now after having used them for a couple of rides I noticed uneven pad wear and on closer inspection after taking the pads out I realized that
a) the pistons now stick out quite unequally, both front and rear, on different sides
b) the pistons travel unequally; as if the one side goes first, then the other catches up, only to stay behind to the first one at the end of the travel.

I could screw in the one piston which stuck out most a bit more with the pin spanner but stopped when the resistance got too big, though it didn't really seem to be loose in the first place.

Any idea why this is happening? Did I mess up with the bleeding after all, do I need to screw the pistons in stronger or lighter or is there some other problem?

 

[thetho]

Solved! For the record if anyone else encounters this issue: Originally, I had one NOS and one decent but old piston installed on each brake and one guess was that the new springs of the NOS ones could be stiffer than the old ones and hence the old ones would move out further and faster. To check, I changed sides of the pistons in one brake and again the old one went further and faster, now on the other side. Pairing the NOS ones and the old ones solved it.