As per my post above David, have you tried running through all the gears (no cables attached) at the gearbox end? You might get a direct sense of how it feels then. It's well worth getting someone to run through the gears from within the car so you can see where your '4th' is at the tower end. It's a real head-scratcher otherwise!I've tried that and it hasn't made any difference. (double de-clutching) So I come down from 5th gear and it gets to mid-position and that's it! It is just like there isn't a slot for 4th gear! Even some force doesn't get it to go down to the 4th gear location. So the only way to get 4th gear is up into 3rd and then down into 4th. As I've said, every other change seems possible, up/down, it's only that one that is impossible! So it's tower replacement next. I've got the latest tower, so I'll also need an associated cup. Details are in this thread : https://www.a2oc.net/community/index.php?threads/new-vag-tower-shifter-help-required.41276/ Let's see what that does to get the gear-changing fully functional ....
Also, I was going to ask: how does one remove that shifter assembly as you've pictured?