Guild Wars 2

Expected:
While using a full set of Superior Runes of the Trapper, once a trap is placed on the ground, you should get superspeed and stealth. Being interrupted, changing weapons, or starting a stomp should not deprive you of superspeed and stealth once the trap has been physically placed on the ground and the ability goes on cooldown. If interrupted, either the trap should not be placed and the ability should not go on full cooldown, or else nothing should prevent the superspeed and stealth once it has been placed.

Actual:
If you are interrupted, change weapons, or start a stomp during the small window immediately after having placed the trap but before the trap arms and procs superspeed and stealth, you do not get superspeed or stealth, despite the fact that the trap is placed and the ability goes on full cooldown. This makes traps feels buggy and unreliable, and does get you killed in battle in a way that feels unfair, rather than due to skillful play on the part of your opponent.

Notes:
I am using Thief traps, specifically. I have not tested this with other classes yet.