The earlier ones are actually less trouble to deal with than the ones you can integrate into pool/spa controllers.
Best bet will be for you to troubleshoot your junctions first, it sounds like it gets full power at first but then drops off due to a short, bad connection or something.
LED's really don't require much current to drive them at all, so it sounds like you're incurring a voltage drop somewhere, they wouldn't draw enough current to create any kind of arc to further reduce conductivity.
If it's not a bad connection, maybe open up the power source and take a look to see if anything abnormal is showing in there.
Sometimes it's as simple as a spider web in the wrong location.