Leaking portable A/C unit...

I have an SPT WA-1220E Portable A/C unit that is leaking when running. It will auto shut off when it detects it is full, but Im wondering if it is filling before it shuts off...? It has a rubber plugged release tube where I drain the water, it drains fine and is definitely not plugged up. I also tip it backwards to get every bit of water that will come out of the drain. I then replug the drain tube. I turn it on, it runs perfectly, cools the room, then an hour or two (sometimes more...) goes by and when I check the area the right side (when facing back of unit) is starting to leak water from the bottom of the unit. Near as I can tell it seems to be coming down from the back right wheel area. Im tired of towel drying and using a hair dryer to dry the carpet. This thing runs fine, it cools the bedroom well. I purchased it used and have no manual and know nothing about A/C units. But, Im on the verge of taking the outside covers off, to see if it has a loose hose or a bad water detection sensor, if there is such a thing...? Would appreciate any assistance !