It had been working fine up until the Pilar vortex. They were gone for the week surrounding it, and had no issues beforehand. The house was kept at a reasonable temperature as well during the time in question. No litter, or obscene amounts of TP being used. The gutter apparently is routed into that pipe as well, but the rain ended well before freezing temps hit.

One toilet flush is what sent water into the walls, and the ice blockage at the blow out hole was discovered.