Okay, technically it’s possible that the first (or a few) tick fires faster than all the functions after Begin Play are executed; what I can suggest here is set a gate after Tick and open it when Return Vector is set.
Second, you’re setting Speed Proj to -10 in both cases, I don’t believe that should be that way. Moreover, just for convenience, you can feed both Set Speed Proj nodes into one and the same Set Return Vector node; it’ll work just fine with less nodes in the screen. Provided that you set X to 10 and -10.
Third, why would you use tick there? It will only work once, since every subsequent tick will do absolutely the same, placing the actor at the same point, because you only do the math once at Begin Play, the Return Vector won’t change anymore; if you want you move your actor by 10 units every tick, the math has to be placed after the tick itself.
So what you can do on Begin Play is only determine the sign, and do the rest by tick.
To do it even easier, you can do this:
