Could this be happening because of static electricity buildup? Very improbable to happen, but still a chance. I wipe my powder measure reservoirs with dryer sheets every year as a standard precaution. 

Even my Ideal #5 black powder measure gets the dryer sheet treatment before use. This has the hammer on the front and each drop gets two flips of the hammer to charge the case and one flip to assure the powder has dropped from the tube.

The RCBS, SAECO, Lyman and Harrel powder measures have all been used without a problem. I check each case with a light before seating bullets even with the Dillon 550. I've been on a range several times when a gun blows up and do not want to be the center of attention if this were to happen to me. 

Unique has never given problems, it is my go-to powder  for .45 Colt and medium loads for the .44 Special. Having three different frame strength .45 Colt revolvers, the bulk of my loading is 6.5 grains for the old frames and 8.5 grains for the medium frames.

Am using a Hornady Lock N Load powder measure.
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Mine has the adapter that mounts on ones press (I use with a Redding Boss). Simply put the case into the press, stroke the handle and it cycles the charge into the case.
Was apprehensive about it throwing small charges with any accuracy as I needed 7gr of H110 for my 25-20WCF CLA loads. I figured, what the heck, I'll give it a try and cranked down on the adjustment. Loaded 250 cases, weighing every 10th throw and it was accurate to within 0.08gr, which was a very pleasant surprise. Have used it with cases from the 25-20 up thru 30-06 very successfully. Works much faster than a ChargeMaster and just as accurate. Have toyed with the idea of getting the micrometer for setting the volume, but it has worked so well with the coarse thread that I've not bothered.

i have used unique in my cast bullet rifle match shooting for over 30 years, and found that the small weight difference couldn't be seen in my shooting.  Now i have shot Milatary rifle matches. As i have such a good relationship with unique i was wondering if anyone uses it in breach seating loads for the 32-40. When i first got my CPA rifle i tried to work up a load ant pressures were so low i had blow back that ruined the cartridge cases. In the 38-55 i have actually shot a few honest 1 inch groups with my marlin cowboy model 336 and unique powder. It has a lyman peep and aperture front. That was before a heart attack, cancer and arthritis in every joint. anyway i have more sr4759 than unique but would still like to give it a try if i could find a safe load.

Great topic.  Just tonight I loaded up 25 rounds of 38-55 with 10 gr. of Unique.  I've always avoided Unique because I never could get consistent charges with the stuff.  Big flakes, in my opinion.  So I double bumped the handle on the Harrels, trying for better consistentcy.  I'll know soon if it worked.  Mike