20 # Propane Tank Stinky! Leaky OR Not?

I just filled up some older tanks about 10 years old. It was a young kid who filled them up. When I got home one tank was sweating at the valve, since I have kept a close look see. I plugged them with the safety transport plug and seems ok. This will most likely be the last time I use these tanks. Is there any concern for danger. Seemed like the leak was coming from the opposite side of the fill/drain valve like a pressure relief valve. Is there any chance the young kid just over filled them and they needed to release a bit of pressure from the jostling ride home??
thanks

 

Answered in another thread. If the tanks have an OPD valve, he couldn't overfill them. ie. Overfill Protection Device. Exchange it for a newer tank. Valves go bad.

 

I thought they blow off fully open? Possibly I am wrong.

 

Don't know, but it makes sense. I never have them filled. Always exchange at HD. Gas company has regular hours. Football games and the like always happen when they are closed.