We recently found a split system AC that had several ounces of water in the copper refrigerant lines. Suspecting that a contaminated tank of refrigerant had been used by a previous tech would be a reasonable theory but after inspecting the system we realized that the evaporator coil had a large leak on the very bottom row. The hole was immersed in the condensate water filling the evaporator pan so when the charge was lost, the hole allowed water to siphon into the system.