Build 'not run', why?

I created a support request some hours ago, but after a few hours (4+), I turning to the community for help.

I’m seeing a spate of ‘not run’ badges on builds. It’s not infrequent, 29 of the 90 most recent builds have it. It’s happening to multiple projects. It’s not confined to ‘OS X’ builds.

Is anyone else seeing this? Is there something I can do on my end?