P: Alpha channel not rendering correctly in smart objects - crosshatching/translucent glitches

I use smart objects all the time, and as of recently, I've been noticing problems with how they render. 
See the image here http://i.imgur.com/fzbzs9q.png

This is a PSD file placed into another PSD (as an external smart object). You can see the dotted pattern that occurs in it. If you look at the extra-zoomed pic on the left, you can make out that some of the pixels are actually translucent (you can see Photoshop's checkered pattern underneath them).

That's the problem - not all pixels are rendered as 100% opaque, even though the pixels in the source image are opaque. And the ones that are rendered as translucent are done so in some sort of pattern, resulting in these visual artifacts. If I create a layer of solid color underneath the smart object, the problem is no longer visible. 

I'm not sure what this problem is caused by. It might be something I'm doing wrong, though I can't think of anything new in my routine to have caused it (and I've used smart objects for years). Perhaps it's something to do with one of the more recent updates. I've also noticed that it seems to only happen at 16bit and 32bit modes. 

Here's another example - this time from an embedded smart object. Notice the irregular crosshatching on the buildings: http://i.imgur.com/npkhsy0.png