Clips displaying low resolution

My question in a nutshell: my AVCHD footage looks low res in the Event Viewer, no matter what display settings I choose (or at least I can think to try). Does FCPX have a problem with AVCHD footage? Anyone else had this problem?

Specs: I've imported test footage from a Canon C100 into FCPX 10.3.4. It was shot AVCHD PF 29.97 at 24 Mpbs LPCM, 1920x1080. So it's HD. I'm running a 2013 MacPro with OS 10.12.5 and 64GB RAM and an AMD FirePro D700 graphics card. So I should have plenty of firepower.

But in the Event Viewer, no matter what setting I choose (View: Better Quality, Original/Optimized), it displays as low res. Here's a crop of a screen grab from within FCPX:

Note the overall blurriness and jaggies.

But oddly, when you export a still from that same clip, here's what you get:

In other words, the true resolution. If you open up the clip in Quicktime it's the same: high resolution as you'd expect.

So what's happening inside FCPX? I've tried generating an Optimized version of this clip, but that didn't change anything. I tried placing the clip on the timeline and rendering; still jaggy on screen. Some setting in FCPX I'm missing, and if so, where? Is this a bug related to AVCHD, perhaps?

An added twist: the same target shot with the same lens at 1080 on a Canon 5D MarkIII displays just fine...

Thanks for any insight you might have...