Why does the right indent overlap with the left indent in the editor?

I use RoboHelp 2017. When I open content in the Design tab, the content appears written one below the other like so:
Heading 1
This is sample
text and the whole
content appears so.
When I double click the right-indent place holder in the ruler, the text spreads across the page like so:

Heading 1

This is sample text and the whole content appears so.

When I close the file and open it again, the content is back to being one below the other.

This does not have any adverse effect on the output. The webpage properly displays the content. How can I rectify the settings in the editor so that the content becomes easier to edit?