You've lost fluid. There are 2 areas the robot leaks from - the gear selector actuators (2 solenoids) and the clutch actuator. The clutch actuator will have have weepage around if it has been leaking. If the gear selector actuators are leaking, the leaking fluid builds up towards the gear position sensor at the front, and will show weepage.
Mine has weepage around the clutch actuator, but it's currently behaving itself.
It's interesting you can still change gear manually (up/down) when hot, which suggest the robot is working ok.