The 5th is there as a secondary/emergency means of landing the Sabre 2. Your primary landing method is by using the stall handle/brake crossover line as you have been. Using the 5th line on the Sabre 2, unless the winds are pretty steady and mellow, can result in a minor mess. Coming from an LEI background it will seem pretty daunting at first but with experience the bridles become pretty familiar and surprisingly simple. As joriws points out the trick is recognizing REAL twists and knots vs. things that LOOk like a twist or knot. If you do have to use the QR and 5th line and pack it up messy, just remember when you go to sort it out not to pull anything tight or disconnect anything. (nothing was disconnected to make the mess so you should be able to reverse things without disconnect) Massage the messy lines and loosen them up to open things up. Take your time and be patient.
If you are parking the kite for a while, park it off the center of the stall handle to an anchor. We use Ice screws here 90% of the time as we operate on lakes (http://www.hardwaterkiter.com/ice-screw ... ashes.html
). If you leave the kite parked too long it can roll over, reverse launch etc. But should be relatively simple to untangle if it does tangle. Anchoring on the 5th line tends to make a bigger mess in wide shifts in wind direction.
The biggest factor in causing a mess when using the 5th line is how the bar reacts as it moves away from you. sometimes it can flop around a bit in the air before it stops and you can get line inverts and twists. The easiest way to avoid this is to keep an eye on the bar and watch what it does as the 5th flags out. And reverse the twists and bar flips when you reassemble the system. Not always easy when you hit the QR in a panic or in a crash.
I haven't flown a Sabre 2 in some time but I don't recall anything that resembles a leash from the CL to the stall handle in the system. Can you post a pic? The 5th line comes down to the trim assembly to the CL and has a ring for your leash. I can't think of anything that mates it to the stall handle and the stall handle would hit the bar before the 5th could fully engage if what you describe is what I envision.