I second the Hummm with both motors. The lube bottles have a one way valve in the top cap. The valve allows air to come in but not out. If the cap is left off, when the drive heats up the lube will over flow. The valve keeps pressure in the drive and therefore the lube does not expand much if any. So if both valves have gone bad, they will both leak.
The test of this is go for a good run, then stop and have a look. If the lube bottle raises, the cap needs replaced. Otherwise, my next thought is the base of the bottle is leaking under pressure