Have you access to another KX49 to see if they ALL do it?

And do you have it in a MIDI loop? Try disconnecting any MIDI ins it has, see if that gets rid of the problem.

Check to see if it doesn't have a 'trigger key' that changes modes on maybe external gear values.

And lastly, try to find out if it has a 'reinitialize' function, and perform that... (after backing up any user data)

Hope this helps.