Hi,
I can't reproduce it in 5.1.10
What to say?
1. The 4.x. branch had a really bumpy start.
Your version is more than 15 month old.
There was the "new" relaunch with the 4.4.Release Candidate
Therefore the advice is: "update"
2. This built in "statistic" is not thought to replace your final analysis, which you do with a statistic tool like SPSS, PSPP, R, or EXCEL, OpenOffice, or..
The Limesurvey "statistic" is to have a quick overview during fieldwork.
Nevertheless this seemed to be a bug which is annoying
Joffm