On the 8FGCU25 where we found the green crud, after cleaning it up everything began working normally again.
But further gossip filtering to us from dock personnel discloses that some operators had experienced loss of mast hydraulic functions as well as wheel drive on that truck. But they are saying that the problem would appear and then disappear if you cycled the key switch off and then restarted the engine. But the problems would recur pretty soon. It finally came to the shop and we started searching and that's when we discovered the battery acid issue.