i just read the peugeot repair manual and they say to remove the head nuts in a criss cross fashion to avoid warping! i don't know weather they ment the head or cylinder? and not to touch the skirts as they are extremly fragile, and the piston only goes in from the bottom.Check out page 27.
like i said barring any damage/wrong parts I would assume it's a temp. difference i'ld get an a/c unit and cool the motor piston and slightly heat the cylinder with a hair dyer or something don't do anything destructive like honing.Jim