Hello,
In the current version there is a logic which tries to resize proportionally the columns when the results panel width changes so that there is no empty space left on the right.
In the new version there is a setting to turn off this behavior, and the columns will keep the exact width as set by the user. This setting didn't make it for the beta release, but will be included in the final 8.1.1 release coming soon.
Jogy