sounds like your spindle recess has become rounded.
take your handles off and inside you will see a square hole (some have two, the bottom one is for lever/lever operation, the top one is for lever/pad operation).
your interested in the bottom one if there are two. i`ve seen alot where an 8mm spindle has been used in a 10mm recess causing a slight but significant rounding off. the answer is to use a 10mm spindle; however you may need to replace the handles if they won`t take a 10mm spindle. google `upvc handles` if this is the case and some will show you what you need to measure.
however the first thing to do is whilst your handles are off insert one loosey with the spindle attached and see if you can move the latch all the way in
levi lewy, July 2010
