RStudio doesn't scale to my resolution, too large windows

Hi, I'm using RStudio 1.1.453 on my Linux Mint 18.3 Cinamon edition and everything was fine when I installed it, like on my old Ubuntu PC. But recently when I've opened RStudio windows were too large like never before. I cannot zoom it out more, it says that it's 100%. I cannot even save my settings, because of too large window. Did someone have a similar problem and managed to repair it?

Did you by any chance update your OS recently, or perhaps update your desktop environment or were trying out a different theme or something similar? It seems as though the operating system is setting a dark theme on some of the RStudio UI elements, and as far as I know this is outside the control of RStudio.

I think, I didn't. I use theme called new-minty but I've got unchecked option to set dark theme in applications.Selection_0101