But I've still had this same issue going back several versions.
I have 2 monitors on my computer. one is my laptop screen and the other is a larger 22" screen. So the larger screen is much higher resolution:
Step 1: open vnc and connect to a server. The initial window always appears on my 1st monitor:
Step 2: I drag the window to my second monitor, and as you can see in this image. I can scroll down just fine.
Step 3: If I expand the window, black bars appear and I can no longer see the bottom of the ultravnc window