Yeah, it definitely happens sometimes. I believe what is happenning is, when someone initiates leap on a you, it will keep you locked from doing any actions until all the calculations are done, you dont get stunned but it will not let you take any actions. So you sit there an extra 1 second until everything is registered. It is same as when a DK ressource NPC pulls you with chain, you slowly travel to them, have to wait until the actual animation ends and all calculations are registered to be able to take any actions. Severity is depending on how many actions going on around you at that moment, how busy the server is with calculating everything.

At the end the server wants to decide if you will get stunned after the effect ends or not, but when its busy, it takes its time to decide, letting you still get damaged in the meantime. Even if you are in cc immunity period at that time, you will still get locked until the server decides that you shouldnt be stunned and let you go. That is at least what it feels like happenning to me.

Leap is kinda buggy, and players using leap since long time probably can judge if a leap will lock a player more than the intended period, due to the server conditions at that moment/area or other parameters that i dont know exactly, that is why it looks like some players can pull that effect more frequently, looks like an exploit. It is similar to how Undo Skill is functioning, it is so buggy that you have to know when and how to use it for it to function as intended, or sometimes you can turn its bugginess to advantage if you use it under right circumstances. For example when you are attacked by a huge group in a crowded area and you are sure people dont have too many AoE attacks, it makes you untargatable for like up to 15 seconds, you can then just sit there spam shields and heals for the whole duration, while server is searching for where you were 4 seconds ago and trying to place you there.