isx cm2250 enigne brake

[hct5]

alright so the truck is shutting down with a fault code 3253, but all the testes pass. it says in the possible causes that Excessive engine oil or diesel fuel being introduced into the exhaust system from the engine could be the issue. the driver stated that it only dose it when the engine brake is on. pulled the valve cover and i found 2 engine brakes that when pushed down onto the valve they do not spring back. could this be the issue ? they are sticking down keeping the valve open and letting excessive fuel into the exhaust system?