With the release of the 6.0 beta (shown here is 6.0b2), you've added new rulers to the top and right hand sides of the graphic/image being displayed/edited.

It's a great feature, but it seems that these rulers have broken the window resize function.

Here is an image shown prior to any edits.

The following preference settings are noteable:

General: Window Content Settings
- Default Window Zoom
- - Always use 100%, scroll large images

General: Display Windows Settings
- Resize Window After Scale/Zoom (checked)
- Show Rulers (checked)