thick red render bar indicating 'unrenderable'?

I noticed this thick red render bar appear:

FCPX wouldn't render the transition I placed under it (not shown). Behaved as if the transition wasn't even there. It seemed to be caused by a hold on a ramp on a compound clip? I removed the ramps and the bar disappeared, but then I placed them inside the compound clip and the red bar reappeared in the same place, but shorter, at the end of the clip. I worked around it but holding the last frame longer, and then trimming the compound shorter (before the red bar).
PS deleting the project render files didn't help, I tried that first.
Just posting because I saw others had problem but no one got a screen shot. It's never happened to me before, and I'm not worried it will happen again.

PS I'm using 10.1.1

Did I say I wasn't worried?
Red bar disappeared, then I placed transition, and it reappeared over start of second compound clip:

Can't seem to work around this...

Technically, those red bars are not supposed to show up at all, but an occasional bug lets them peep through.

Is it adversely effecting your playback at all?

Under the red bar did not render so that any effects were ignored. So in the second instance (pictured immediately above), the first half of the transition behaved normally but the second as if there was no transition, just an abrupt change to the next clip. BTW the transition was a 'Bloom' dissolve- I suppose a cross dissolve would have been red over the entire transition.
From memory, I solved the problem (sorry didn't note exact steps) by replacing the timeline instances of the compound clip with fresh instances from the event browser (or something similar, I vaguely remember it was a bit more complicated). The problem seemed to be that FCP wasn't updating the timeline, or was getting confused between different instances of the same compound clip (I had been updating it in other projects).