How to reproduce:
1) Either try this on OS X, or you need an installed Zapfino.ttf. (Sorry, I'm not aware of a free font that triggers this issue ATM.)
2) Open Writer.
3) Type "llll".
When you type the 4th "l", it's only painted partially, see the attached screenshot.
A workaround is to click on the header area, which triggers a repaint, and then it gets pained properly.
Created attachment 98695 [details]
How it looks like currently.
Created attachment 98696 [details]
How it should look like.
Miklos Vajna committed a patch related to this issue.
It has been pushed to "master":
fdo#78444 sw: avoid incorrect right shrinking of repaint rectangle
The patch should be included in the daily builds available at
http://dev-builds.libreoffice.org/daily/ in the next 24-48 hours. More
information about daily builds can be found at:
Affected users are encouraged to test the fix and report feedback.