I have created six groups each having 5 question. While adding questions I made sure that the random option is off, even the questions code are unique and in an order as I wanted them to be in a fixed order. For example if I've added questions in group 4 then many a time the question order changes in the previous groups. This behavior is highly inconsistent making it harder for me to understand the reason of this problem. Is it a bug? or something I might be doing wrong while adding questions.
(Note: I've installed limesurvey 4.2 on my server using Bitnami)

Where does the question order change? In the front end when taking the survey or in the back end.

Can you provide screenshots and a sample survey (.lss file)?

Do you have something in "randomization group"?