(Posting this again because the system ate my previous bug report)
I've been noticing that abilities have a tendency to not apply or queue correctly, usually during intense combat, server lag, under cooldown affecting debuffs, and/or while using the Gatling Emitter. This is a separate bug to the Gatling Emitter, and predates it, but was very evident while using the emitter. This affects most/all abilities, but some abilities, possibly due to the time it takes for them to charge up, have it worse (such as Trajectory Bending). I don't know if this affects key-bind users, as I prefer clicking.
I managed to capture the bug while doing a synthetic test, having to go back and click on TB a second time after it failed the first time.