Comment 22 for bug 348353

I saw process_rewind errors like that when the rates didn't match between Alsa and Pulseaudio - is everywhere using 48000?

Is Pulse definitely connecting to the rate converter and not directly to the A52 filter?

Is Pulse itself definitely using 48000?

Failing that, you can try copying Pulse's default.pa to your home directory, deleting the udev stuff (which will stop profiles working) and putting just oen sink for test purposes:
load-module module-alsa-sink device=a52 rate=48000 channels=6 tsched=0 sink_properties=device.description=SPDIF sink_name=SPDIF
load-module module-suspend-on-idle timeout=0

You can then put pa_sink_set_max_rewind(u->sink, 0); instead of the if else (as there is now only one sink) to be absolutely sure that max rewind is being set to 0.