aquapolis treasure hunt room barrier bug or fail

There is a barrier on every room in aquapolis given with a timer before it closes. this barrier is like a mini duty instance for the party as well as a timer so that the rest will quikly enter inside when boss is already pulled.
The same goes along with aquapolis there is a barrier in every room you engage on every open door. For Aquapolis there has been a bug i encounter that automatically fails the duty, when a mob monster suddently walks off the barrier line moments before its sealed. but in this case monsters can leave away the barrier line right before it closes. Now how exactly can that happen? On specific classes players use with a knockback skill.
One for example the summoners class two skills that they have: Backdraft, and Shockwave. both skills not only does wind damage but also gives a 15-yalm knockback of the enemy I would encourage so that Devs can resolve this issue of the barrier