Yes, using the Area populate brush, no constraints. I had tried applying some falloff, but turned that down to 0. And yeah, am on the latest build. This is so strange, and making me crazy. Painter is virtually unusable as is. 

 

What do you have your "draw" settings set at in the General Options (ie plant instant draw, etc.)? I'm at the default settings, which are Instant Draw - about 1/3 way up the scale, and plant instant draw, a little less than instant draw setting - maybe a 1/4 way up the scale.