Figured this out last night when I was playing.

If you are by a EMP or get hit by a EMP grenade, Aces and Eights will have a chance to stop working if you flip the Aces and Eights buff from the gear set.

Flipping Four of a Kind and Full House will keep the set working, but flipping Aces and Eights will stop the set completely and the only way to fix it in game as far as I know is swapping builds/loadouts.

Only way preventing this from happening is to not use your Marksman rifle to flip any cards and use your secondary weapon until you are no longer getting hit by an EMP.

Here's a clip of the set working with the Four of a Kind and Full House card flips while under EMP status effect, but breaks with Aces and Eights get flipped. https://streamable.com/9qcop

Not sure if this is a Xbox only problem but I figured this would be tested on the other platforms as well.