Translation Results Window Width

Since a few days ago, I cannot change the width of the Translation Results window in SDL Trados 2015 SR2. In fact, I am able to adjust the window, but not the "internal margin".

Please see the image below to see what I mean:

The option to reset the window layout did not help.

I am (almost) sure that there is an easy solution, but it's been a few days and I cannot find it. I would appreciate any help.