I have had no combustion problems with Universal. I use it for two of my standard loads:
1) .40 S&W, 5.9 gr. Universal, CCI500 primer, 165 gr. Rainier bullet. Very clean, very uniform velocities (@1100 fps), but not near max. NO unburnt powder
2) .45 Colt, 7.9 gr. Universal, WLP primer, 250 gr lead FP. Very clean, very uniform velocities (<800 fps.). NO unburnt powder. This load is intended to duplicate the classic 8.0 gr. Unique, which it does, but is much cleaner.
I have stayed away from Universal for use in the .45 ACP. My standard load (4.3 gr. Clays, WLP primer, 200 gr. Rainier FP) has nearly ideal characteristics in my 1911, and is softer recoiling than my previous load of many years, 5.3 gr. 231.
I believe that the other comments on this thread are pretty much on the mark as far as trying to load down this particular powder. I have never tried loading down Universal, so I have no personal experience with doing that. Some powders seem to have a much wider load range in a particular case than others, but I don't pretend to know why.