I have this problem specifically with my Carrier Rooftop units. They work great and are as good as can be until they start leaking water though the controls in the ceiling unit....
CLEAN the FILTERS...
When the filters get clogged up (they may not look bad) the pressure drop across the filters keeps the condensate from draining out the hose that are there for the purpose and the water splashes up and into the air discharge hole.
It was a bear to find because it won't happen with either cover (inside or out) off.
Matt