Room Combine Processing Block Causing Distrotion

I have a room combine processing block handling a 4 room combine. When all the rooms are separated my Source output is clean and sounds great. Once I combine one room I begin hearing distortion when the metering reads around +10dB. When I combine 4 rooms the Source output begins distorting when the metering reads 0dB. I'm at a loss as to the source of the distortion since all metering is under clipping all the way from the analog input to the amp. Has anyone else experienced this and found a solution?