HELP! Eaton STC Connector Will Not Release

[brdgbldr]

I need to replace two oil cooler hoses. They are the EATON STC (AEROQUIP) connectors. I bought the special release tool and the first connection I tried came right off. Two other connections took a lot of wiggling but eventually came off. The fourth connection will not release. Maybe the release ring is messed up or the catch ring, but either way any tips or tricks for these would be very appreciated.

 

[brdgbldr]

Update... I finally got the hose to release.
For those that are interested, the "special" tool is made to be the perfect thickness to push in the release ring just the right amount to work. The problem is that they cover the release ring in rubber which deteriorates over time making the tool too thin To do its job properly. Shimming the tool (I used two small screwdrivers) pushed the release ring in far enough that the hose just pulled right out.
Live and learn. Now I'll probably never need this knowledge again.