Moving a Pharo window under Centos

I’m trying out Pharo on Centos. Since I don’t have a spare PC that I can install Centos, I installed on my Mac under Parallels. Centos runs fine, and I was able to install latest Pharo 8.0. With any other windows under Centos I can grab the title bar, move it, then drop it where I like. However, inside Pharo, any window I grab by the title bar, though it moves to follow my cursor, Does not drop when I let up on the mouse. I’m then stuck where all I can do is drag that window around but never drop it. For some reason when I Cmd-tab away to a Mac App, then move the cursor back to Pharo it only rarely fixes the problem. Anybody else run Pharo under Centos, under Parallels? Anybody else seen this? Is there a fix or a workaround?