D7e loses steering after warmed up and shutting off

After running my d7e for extended period Of time if I shut it off and then go to start again sometimes it does not want to steer it will go forward and backwards just fine the pressure gauge on the dash will build pressure when I pull the steering lever then let off the gauge will drop to zero and bounce back up if I shut it off several times play with the shifter in the steering and the foot pedals usually I can gain steering back only after shutting it off and starting it several times I don't know if I have a relief valve hanging up or not my pump pressure seem to be okay any help or previous experience will be greatly appreciated

Did you clean the oil streaner magnet and if remember he was near oil filter

The machine had a full service less than a hundred hours ago strainers filters and all it steers fine all day long never has an issue it's only after shutting the machine down and trying to restart if I leave it running it will never lose steering

Hi Team,
alas, this poor photo copy of I think a Service Reporter article on said subject I received at a Cat Trans. School back in Oct. 1965. Have searched all of my Lit. for an original in other type publications as well to no avail.
Hope this helps.
Cheers,
Eddie B.