Cleanup Task quits immediately

I've just installed the Cleanup plug-in from the SDL appstore, so I should have the newest version of this plug-in.

My Studio version is:

I'm trying to convert this sequence to one mark-up:

(This sequence is representing a bullet.)

When I select the Cleanup Source task from Batch Tasks, Studio quits as soon as I click the Next button in this dialogue box:

Surely I must be doing something wrong. But what?