Blending Modes 'Jumping'

This has been driving me crazy for a good year now so I can't just blame one version of photoshop, however whenever I apply for example a 'Multiply' to a layer the menu jumps to a completely different blending mode (luminosity seems to be it's favourite).  At first I thought I just wasn't being careful when applying but even when I KNOW I'm being careful it still does it.  And not just to the next blend mode down, it literally jumps halfway down the menu.  Tell me I'm not crazy and this is happening to somebody else too?