Thanks for the reply. I have a couple of items you should check.
First, your machine should have a Crossover relief valve just to the right of the backhoe control valve.
Remove the relief valves (one top and one bottom) and inspect them for trash sticking in the end or ports. Clean as needed.
Next check the line reliefs on the backhoe swing valve. (Follow the lines from the swing cylinders to crossover relief and then to the swing control valve.)
Remove these reliefs and inspect them for trash.
Next, remove the bottom spool cap so you can access the primary resolver check valve. Inspect it for blown seals or debris sticking in it.
Finally, remove the flow control spool from the swing valve. It should slide out easily. If stuck or the spring below it is damaged, you may need to replace the spool, spring and or the swing valve.
I will attach a picture to help you identify the swing valve parts. The crossover relief valve will look similar to the line reliefs of the swing valve.