I did some testing and noticed that the decimal numbers are being rounded here too! However, they don't round right away. If I change the number, then click the focus off from the 3d box object and click it back, the numbers have been rounded in the properties bar.
About the 3d box bug. I wrote this originally to the bug tracker.
I experience this bug too.
Some additional information:
Changing the display settings does solve the problem partially, the
workspace isn't black any more. But display settings have to be changed when Construct is running, otherwise changing settings doesn't have effect. Here, 60Hz doesn't magically solve the problem, but changing the settings removes black.
Secondly, after changing the settings, the 3d box itself seems to be
invisible. Only the "root" is showing up. However, if then more 3d box objects are added, their boxes show up fine.
Also, after changing the display settings, scrollbars become invisible and, quickly flicker, when user clicks the place where they should be. The "layout editor" and "event editor" tabs are gone too. This problem seems to appear even if there are no 3d boxes at all, just changing the display settings triggers it.