I've laid miles of braid in my time and here's what I've learned.
Braid recess should be at least 1mm wider than the braid and a little deeper (0.1mm or more) than the braid thickness, the braid is then laid against the shoulder of the recess away from the slot. This stops the wheels on the cars catching the edges and stops the guide rolling up the inside edge.
When laying the braid hold it above the track so that it loops as it goes down (a picture would help here). The loop forces the braid weave to open a little so it's not stretched, and it can expand and contract with temperature changes. This is critical in corners or you'll end up with Johnno's problem above.
Glue? for almost all of the tracks I've built the braid was laid with contact glue, simply because it was prior to the high bond strength tapes being widely available. Contact glue has the advantage of not being fussy about the surface it goes on and is easy to repair. It's cost effective and you don't need to clean the braid, but it's messy.
High bond strength tape works well, just follow Rick's instructions above regarding recess preparation as a smooth surface is important.
Again, the most important thing is to loop the braid as it goes down to open the weave. Get a piece of your braid and curl it into a circle and see how it opens up, this is why you're having trouple with the corners Johnno, nothing to do with the glue or tape.
Hope this helps.