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.
_________________________
An arranger is just a tool. What matters is what you build with it..!