Hi,
Marcus and Martin basically described all I can tell you with the given info. Many of the given blocks are designed to be verbose about their setup. This is mainly to see what happens.
The buffer allocator warnings would disappear if you would set N_rb_dl = 6. But that's just avoiding the underlying problem. This warning is generated by the blocks between extract_occupied_tones and demux_*. I chose to only pass on the used tones, which don't line up to a power of 2. That also means there is no quick fix for this. But for now it works and shouldn't worry you.