Prevent CommandManager Splitting

Hi there,

When I start "Copy with Mates" the CommandManager is split automatically into 2 panes, with "Copy with Mates" barely showing (I've attached a screenshot of what I mean)

After finishing "Copy with Mates" I can double-click the splitter bar to un-split the CommandManager.

However, the next time I do "Copy with Mates", the CommandManager splits again, and I have to repeat this process.

I tried checking "Lock CommandManager and toolbars" by right-clicking the ribbon and choosing "Customize", but this had no effect.

How can I prevent "Copy with Mates" from splitting the CommandManager?

Thanks!

EDIT: This is in SolidWorks 2018 SP1.0

SolidworksUser Interface