A833 gearbox 4th gear doesn't work

Hi,

My 4th gear is missing and 3rd gear doesn't come out.

First time this happened we opened the gearbox and saw that 3rd and 4th syncro ring pin's have popped out of their place and that's why the 3rd gear is stucked.

We put the pins back to their place and it worked for about 6 km (first few KM I ever drove my car with this gearbox).

Now we opened it again (first time I did it my self and didn't know what to look for).

We have two questions why is this thing happening (the pins pop out)
here is a picture:

https://dl.dropboxusercontent.com/u/19022509/pins.jpg

Second question is that is this normal:

https://dl.dropboxusercontent.com/u/19022509/teeth1.jpg
https://dl.dropboxusercontent.com/u/19022509/teeth2.jpg

it seems that some of the teeth have been cut out (half) ?

problematic parts have marked red.

In my country we don't have a shop/garage who knows this gearbox, so we need to figure this out ourselves.

Any ideas ?