UiPath Studio v2018.4.1
This might not be a bug per se, but it sure is annoying! I have a three monitor setup, two of which are landscape 1600x900 and the third is in portrait orientation 900x1600.
The main Studio window cannot fit on the 900x1600 monitor at normal (100%) scale. It cuts off after the minimize button as the window physically cannot be made smaller to accommodate.
Floating windows do not appear to have this limitation (nor does Ui Explorer).