Succeeding at a skill roll doesn't always mean you achieve what you wanted. Especially when what you're trying to do is being actively opposed by another person. They might well get a chance to prevent, mitigate, or undo what you've done.

As a GM you need to remember this. Your antagonist NPCs have skills too, and can use them to foil what the PCs want to do. This is built into the combat rules of many games (where defenders might get a block or parry roll, for example), but it can pop up in other places too. Don't let your NPCs be saps.

Transcript

Trooper 4: We're nearly there. See, there's the sign my friend Trooper 3 was telling you about.
Luke: Time to close this show down. Force Suggest. Uh oh... 2.
GM: I suggest you try something else.
Luke: Right, I'm gonna try and lock the bikes together. Yes! 16!
{shot of bikes locking}
[SFX]: Kerrrunch!
Luke: I Force Jump off! 14! Another success!
GM: The trooper <roll>... disentangles the bikes and circles around.
C-3PO: You've succeeded! In losing your bike while the trooper still has his.
Luke: So... Turns out you need to have a good plan, not just good rolls.
Han: Whereas some of my plans were so good they didn't even need to succeed!