I re-ran the sweeps in REW with the sample rate set to 48k and went through the process of exporting Impulse as WAV (having run Shift IR function first in REW), selected Mono 32 bit signed, checked Normalize, and Windowed.
Ran sox to covert to 32 bit float RAW format (.PCM) and checked in Auacity that the waveforms match exactly (and the sample rate is correct). Ran the PCM files through DRC Designer to generate a stereo WAV filter file at 48k (also verified in Audacity)
Loaded the filter a> with a config file (stereo at this stage) and b> directly load the WAV filter file into Convolution, Output format was set to sample 44.1k=>48k, 48k=>48k, etc, but still got the same weird output (also verified using Pink PN generator in REW with the RTA running).
For whatever reason it is not working for me. I will try grabbing the Convolutor VST plugin and quickly try with that.
One other thing to note, as a test I went to Output format and set 44.1k=>44.1k, 48k=>44.1k (unusual config, I know) shutdown MC17, rerun without convolution enabled and was able to replicate this same scenario, so it appears there is something amis. Running on and AMD A8 setup - maybe its and AMD thing?