What was the temp?? You are not looking for differential temps top to bottom. When I said FLIR gun, I mean a thermal imaging camera. I realize not many people have one, just saying.
if you let everything cool down, then fire machine, dig bucket into something it won't dig so it is on relief. Note where the piston likely is, sit it on relief for 10-15 sec or so and check for heat on that cylinder around the piston area. On a cold machine, there should be no fluid moving in the cylinder and it should not heat up because the relief should be happening in the valve block.
If you want to use your IR gun, do this test, then just comb up and down the cylinder barrel a bit to see if there is a hot spot. Remember there is a lot of steel there so getting instant thermal response won't happen.