Ok, sounds like you are having water vapor condense in your crankcase, must be pretty humid where you are.
1- Make sure the crankcase has a vent on it somewhere.
2- Be sure you are running the compressor long enough to get the oil hot enough to evaporate any water that does get in there. If the compressor is over sized and just runs a few times a day it may not run long enough to flash off the water that does collect.
3- That unit looks pretty big if you sized it to spray paint with it may be way too big for your normal shop use (see 2 above).