iPad 2 speaker is acting weird!

The volume sometimes closes itself off for no apparent reason. This means that the actual buttons but also the softwarebuttons (in the menuflap if you swipe up) disappear!

If I go into the settings and play with the volume switch that is there it DOES work. Needless to say I find this weird, because it looks as if the speaker is working properly and it's an electronic issue.

Does anybody know how to fix this?