About how old is this unit and could I get the serial number too, please?
serial number is XXXXX
Below is a link that shows the bottom part of your unit. Click on it and look at #8. These unit have a history of the drain pan cracking. You will need to, with the unit unplugged add some water to the pan with out overflowing it and see if it leaks out. You may also look at the metal under the pan to see if water has been there for a while. (white and chalky)
Let me know what you find.
If the water test leaks then we know the pan is bad. It is a pain to remove the pan. Most of the time when the pan is bad it is behind the compressor on the left side where the pan gets thin.
The defrost water does evaporate on its own from the heat produced by the unit.
Let me know how the water test goes.