Please see page 5 and tell me point of leak
You have a leaking collector box gasket.
This is a bit of a job...but you can remove everything to get the cover off. Then use RTV silcone caulk and lay a new bead around the cover flange edge.
Reassemble, wait one hour, then start back up.
This unit is not supported with a service manual
This is a factory issue. Since the unit is only 2 years old call your installer or a Goodman dealer. You may have recourse.
Very simply it was a deficiency at time of manufacture.