(edited by Grogba.6204)
Keep Construct core pushing bug?
I don’t know if they fixed the other bug which causes the orb to get stuck or not yet.
I’ve notified them of it getting stuck in specific areas on that map but that issue to the best of my knowledge still existed up to the last balance patch.
There are specific spots where the orb will get glitched on the terrain. You probably hit one of those spots. This bug existed since wing 3 launch.
The push mechanic on the orb has an in-built cooldown of 2 seconds. If you strike the orb with a CC skill that deals damage, and that CC skill activates the in-built push mechanic, it will use the push mechanic instead of your CC skill. This same problem happens if you mistime Glyph of Tides or Mesmer GS 5. The only reason Mesmer Focus pull works reliably is because it does not do damage, which means it never risks triggering the in-built push mechanic.
tl;dr: You mistimed your LB4 and it activated the in-build push mechanic instead of LB4’s actual push.
As for your other issue, there are certain locations on the floor where the orb will get stuck and not push. It can sometimes be hard to avoid these (and knowing where they are just takes practice) and ANet should really fix them to not exist, but they’ve been around a while and can be worked around.