Brief bug summary: Angelic Buster has a third job skill called "Iron Blossom" and it does not interact well with Kanna's third job skill "Blossom Barrier".
More details:
As you can see in the video, whenever Angelic Buster walks in and out of the barrier, the Iron Blossom effect (knockback resistance) and buff icon disappear from the buff bar on the top right side of the screen. When Iron Blossom is put on a pet Auto Buff the pet continuously reapplies the buff when you are inside the Blossom Barrier. A pet auto buffing can cause other skill inputs to not be registered when casted simultaneously, which in certain situations can be quite frustrating. This is hard to show in a video but definitely noticeable when you are playing the character.
Character Name: ImSoBoosted
Character Level: 275
Character Job: Angelic Buster
World Name: EU Reboot
Date and time of the incident: Can't recall when it started, might have been together with the Kanna rework. Maybe other Angelic Busters can give better information on this.