Oh, thanks. I guess that's the different between Samus' and Link's zairs, Link can save himself with a zair for the edge if knocked away (could in vBrawl at least) when Samus can't.I believe it happens when Samus' momentum is moving away from the ledge when you press Z.
I'm a bit horrid at explaining stuff, but I'll try. Samus' tether beam will stretch out to the exact amount of length needed to snap the ledge at the moment you press Z. Since the beam is rather slow-reaching when you use it, any movement away from the ledge when you press Z may leave a gap. This can happen when falling as well.
I've had this happen with Lucas as well since he and Samus have slow tethers, I think. You can prevent it by making sure you have momentum towards the ledge when you zair.
As for the explode-on-touch morph bombs, I thought they were working on it or is it off the table now?
THANK YOU! :D