Should I not be inputting two balanced signals (balanced stereo) into a single Temblor T8?

I currently have two balanced signals: stereo, a balanced right and left, going from a DI box (XLR) to both balanced input on the back of the Temblor T8 (1/4" TRS). The situation I'm finding is that when both chaels are in and the DI box gain is maxed, I have to have to turn the gain way down on the T8 to avoid distortion. If I gain down at the DI box, and then 0 the gain on the T8 it sounds terrible.

That being said, if I unplug one of the chaels, i'm able to run the DI gain at max again, and have the T8 at 0 gain and it sounds perfect. So what appears to be happening is that its merging the signals, but merging it in a way where it's stacking the signals on top of each other and making the signal way too hot; to the point of clipping. It sounds good with it gained down at the T8 like this, but should I not be ruing it like this? Is it specifically designed for only one chael to be used at a time?