Low-end frequency issues, Master Output mode, DDJ RB

Is anyone having this issue? I don't know what caused its onset but this didn't use to happen and now I essentially cannot use master output mode. 

I'll mix my first couple tracks and they'll sound fine, but within 3-10 minutes this distortion of my low-end creeps in, creating a terrible "blown out speaker" bass sound that only stops if i disconnect the controller. 

I'm not redlining, and I have the most recent rekordbox and DDJ RB firmware (1.03) installed. The issue only occurs in master output mode–– if I'm only monitoring my audio via headphones through the controller's internal channel/master cue it sounds just fine. It's not a specific speaker issue because I have tested multiple. I haven't been able to recreate the problem when playing tracks through rekordbox without the controller, so I'm pretty certain its a controller issue.

I'm kinda disappointed that the firmware update earlier this month didn't fix this issue for me. Does anyone have any ideas? Any settings I should double check? Thanks.