Enabling indentation guides breaks everything for me now, even with Tab indent size of 4, and Indent using tabs disabled.
Without guides:
With guides:
The cursor jumps between the points marked with red by one press of the left or right arrow key (like if the first non-space character of the line got a huge padding to the left of it).
Basically, the guides are unusable at this point with any setting.
1.5.11, Windows