Presets use a Unique ID for each control in your layout. If you loaded saved pages in any version prior to 1.4.4, two controls might share the same Unique ID (bug on page load). This is only used in Presets. The "Fix Current Layout" button will sort out the IDs.
Note: if you've never loaded a MIDI Designer Page individually, this is not a problem for you. In any case, it's ALWAYS safe to run "Fix Current Layout."