Game lags to a super slow-mo mode during breach

Several times while playing this weekend, grouping with another player, we both experienced instances where the game lags into a super slow-motion frame rate and then speeds up to a super-fast speed eventually. In a breach, the game becomes unplayable at time and we could barely move, even when there weren't an abnormal amount of mobs or items on the screen. It was almost like we were experiencing the old desync issues. I then proceeded to run groups with 5-6 people (and the same other person in the lagging maps), and they ran just fine. The slow mode seemed to happen within the span of a few hours and happened nearly 4-5 times in different maps. I'm on the west coast, other guy was on the east coast, california server.

Experienced the same thing today.

Only happened to me once: In the Stone Citadel map.

Wild guess here: Maybe that is due to the size of the map and the amount of monsters in there?

I did play lots of breaches already and it never happened except this one time in Stone Citadel.