Editor problem on iPhone

The editor has suddenly developed a quirk on iPhone when editing a document. When I press return to start a new paragraph, the next line drops below the onscreen keyboard so that I can’t see what I’m typing. I have to the drag the page up slightly every time to be able to see it. Same thing happens if what I’m writing wraps around to the next line. In fact, when starting to edit a document the last line of text starts off noticeably tight to the keyboard, with no gap at the bottom. It’s really messing with the flow of writing.

Happening to anyone else?

It’s an iphone 5 SE running 13.2.1