How to prevent unwanted Copies of Slides in Impress?

When I go to the text box of a slide, then copy the text and go to another slide to paste the text there, then instead the slide is copied.

The way this works: the cursor turns into a pointer with a plus-sign as soon as I copy an entire line of text (not just a few words in the line) and then click on another slide in the side panel. So now I am in the new slide, where I want to paste the text. But no matter where I click to paste the text, instead a copy of the slide is created, because the cursor still has the plus-sign.

So I first need to press ESCAPE to get rid of the plus sign, before I can click on any text boxes. Is this a bug or is it wanted behavior? If the latter, can I turn this off?

The problem is that I copy a lot of lines from here to there and it becomes very tedious to remember that I have to press ESCAPE every time and sure enough, I do forget it occasionally and end up with a presentation with a lot of duplicated slides.