Cat d5k2 blade falling/fast movement

Im coming here for help once again.
We have a cat d5k2 serial number cat0d5k2tkww01017.
Operator says he was pushing on a small tree and thought he heard some kind of "pop noise" around the hydraulic valve body. Who really knows what exactly happened but anyway After this the blade would drop while trying to push a grade also the blade movement is extremely fast now especially down will drop like a rock. Its fast up and down. Went in with et no trouble codes etc recalibrated blade ok ni change went into the valve body the spool for the blade seemed stuck did not move freely like the other valves in the body. The tractor will not hold the blade up engine running or not it drops slow. Raise the tractor up and does the same. Could anyone help me with another starting point or previous similar experience. Thanks

After moving the spool back and forth it seemed to loosen up comparable to the others but it did feel like the was a slightly harder spot. Did not really find any trash or metal in the body. The spring on the spool was ok. No leaks that are visible on the lift cylinders.

John- might consider removing the lines off of both lift cylinders and using shop air to check them for leaks internally. Be sure to check them both ways, I’ve seen the rod break on these dozers.

Ok that was my next move i think. I have been messing with it some and the spool didn't seem to "center" i got that straight i believe but still not right. Oh i also found that one of the solenoid blew the end out of it for the lift function replaced bo change. Ill try to post a picture of it. Hadnt found the the piece yet.

Very small piece in the center