Swiftkey doesn't account for space at end of line in OneNote

I'm not sure if this is a OneNote-specific bug or not (and I realise, from a previous bug report, that OneNote can be weird). I've had the issue in other apps too, but far less consistently.

The keyboard fails to take account of the space at the end of the line if you move on to the next line and then back. 

Steps to reproduce

- Use Flow mode to enter the word "test"; keyboard will insert "Test ".

- Press enter to move to next line.

- Press backspace to move back to previous line. Keyboard now shows "Test" as the current word, ignoring the space.

- Type another word using Flow (maybe "this").

- Keyboard will correct the line to "Ttest this " (with 2 Ts at the start).

The keyboard remains out of sync by 1 character with respect to the cursor's actual location until the insertion point is moved to a new line and back using touch. 

Thanks for any help you can give solving this issue! (And if this is a OneNote problem, please let me know so I can file a bug report there.)