The cause of much frustration and confusion is the date change that doesn't change.
Particularly annoying is when you think its ok and you're all ready watching it (yep i've spent a lot of time studying this!) and you can see it move and it nearly changes...and...it gets to nearly the point of no return...and...then it flips back again!
Sometimes it tricks you into thinking its fixed and then after a few days *!!$$^*^! it doesn't change.
If you haven't worn it for a while and you need to go round the calendar to get to the current date the associated frustration can nearly result in a smashed up Monaco (seriously!)
Nic now knows how to fix this and for the small fee the upgrade is worth every penny and could save your pride and joy from more serious unrelated damage! :-)
AndyO...

: these are my top 10 faults/problems (can be in any order really as
: they are all frustrating)
: 1(cal11)Number 1 for me is the date turning wheel on early cal 11's
: that was made with a plastic tooth. slowly the tooth wears down
: and starts to fail. (Mr Ogg knows all about this one!)
: 2(cal11,12,15) the screw 5443 that hold down the setting lever on
: both 11/12/15 calibers often breaks off due to repeated use. its
: a really annoying thing to happen as it requires alot of the
: movement to be dissasembled to replace. interestingly the
: valjoux 7740 sometimes is seen with a sprung setting lever which
: solves this problem.
: 3(cal11,12,15) every heuer collector knows this one! the 8180
: chrono return lever often can break where the pusher repeatedly
: hits it, sometimes i have seen these re-welded.
: 4(cal11,12,15) the 1143 osilating weight seems to be the first
: thing to rust if water gains entry....its more the tube that
: runs down the middle fixes itself to the 8020 chrono wheel.
: 5(val72) 8270 minute record jumper is pretty fragile on most chrono
: movements and is often seen missing on cal 72's.
: 6(val72) 8221 the pin that hold the chrono reset lever. if this pin
: ever gets bent or goes out of alignment it stops correct reset
: of the chrono wheels. it can be a big problem if the hole it
: sits in is damaged on the movement plate.
: 7 removal of silverstone glass....v tricky!
: 8 monaco sprung case stays.....v annoying if stuck in!
: 9 chrono second hand pin tubes.....when worn are really annoying.
: need pinching to stop any movement when being reset. with
: patience the tubes can be replaced (good challange)
: 10 chrono pushers sometimes break off during removal leaving part
: of the tube stuck inside a watch case covering the thread. this
: is v annoying and then often has to be broched out slowly to
: save the thread from getting damaged.