The trigger_push you have above the trigger_catapult is in the wrong direction. You can set the direction with the 'Push Direction' keyvalue. It looks like you tried moving the origin of the brush to a direction instead.
Can see here that 0 0 0 faces sideways, which is why your catapult is pushing you slightly sideways:
If you use rotate this teamspawn guy towards the direction you want, you can then copy its Pitch Yaw Roll into the move direction of the trigger_push: