Problems with brush adjustments

Lately when using brush adjustments, mask overlay just won't show. Normally pressing O on the keyboard worked but it doesn't. Sometimes I can't even select previously made brush adjustments anymore because the blue circles don't show up. But if the blue circles are there and I put my cursor on it the red mask overlay is visible. Only then. It's really random and I don't know what I could do about this. 

I use Lightroom desktop version 3.3 on Windows 10.

Was the brush adjustment tool changed somehow or is this a bug in my program?