The moderators should feel free to remove this post if Serif is not to blame.
Yesterday I copied some text from APu and pasted it into the JCE Editor from Joomla. Everything looked good so far on various destop browser, but in Chrome for Android several crossed rectangles appeared at the end of the text.
EDIT/FOUND OUT: Obviously these were the paragraph breaks. Some editors had no problems, some editors had problems. Seems to be that APu is behaving correctly.