This is a weird one, but I've had it happen twice now on my Savage/Shield Brute; it seems it's related to activating the power out of range and then moving towards your target, relying on the queued power to trigger once in range. Both times I would run forward, the power would activate and I would end up being where I originally queued it, rather than at my destination. The second time it happened it also appeared to consume 90% of my endurance in the process.
There's a secondary issue where sometimes the teleport will complete, you'll do the attack animation, but nothing gets hit (nor are there any miss indicators). It might have to do with using it whilst Hovering and/or height of the character? I only started noticing it after I upped my character height to near max, and a friend of mine has it happen pretty often (likewise a very tall character, but they also use Hover).