6820 automatically went into speakerphone mode

My 6820 was closed (the keyboard was folded away) and when I made a
call, it automatically went into speakphone mode. I tried a few calls
and they all did the same. I turned off and on the power and then the
phone was normal again (no speakphone unless I specifically wanted it).
Is this a loose switch problem? Any other encounters like this anyone?

Thanks.