Sigma Photo Pro 6.6.0: Bug with GPU Acceleration Mode and dp Quattro

There seems to be a bug in the latest release of Sigma Photo Pro (6.6.0) at least with the
following hardware:
Mac Pro 2010 - 12-core - ATI Radeon HD 5770 - Sigma dp0 Quattro

If the GPU Acceleration Mode is active, there can be color loss in certain areas of
the image.
This happens especially when some chroma noise reduction has been applied.

If chroma noise reduction is set to the far left position, the problem is gone, but there is still a
very slight reduction in color saturation apparent.