Hydraulic jack repair

I have a Craftsman hydraulic floor jack that won’t release the ram once its pushed in/down. Anybody repair one of these before? Its a nice jack and when it works, it works great. Puts my other jacks to shame.

And yes I went to Sears and they don’t warranty jacks like they do tools.

got the same jack,mines just low on fluid.what kind of fluid should i use???

After doing some quick research, one site says to use Mobil DTE Light or DTE 24s or Shell Turbo 32

Appears my jack may have a bad check valve.