125psi could be fine, depends on what the other cylinders tested at.
Cold engine
With all spark plugs removed
each cylinder in a 4.0l would be about 155-165psi with a calibrated pressure gauge.
With all spark plugs out starter motor can get good crank speed, we are dealing with a metal to metal air seal, so for sure not air tight, and it isn't suppose to be.
So slower crank speed allows more air to get out which lowers compression numbers.
Like adding oil increases compression numbers, blocks more air from escaping passed the rings.
And gauge could be off, doesn't matter if you are testing all the cylinders, because all would be off by the same amount, and compression test is not strictly about a high number, its about comparison of the numbers, if 5 cylinders tested at 130psi and #5 at 125 then all is well, then I would check the gauge, or timing chain, lol.
If you just test one cylinder and leave other spark plugs in then 125psi could be fine.
If you can test the others and #5 is low then add a teaspoon of oil thru spark plug hole and retest.
It will always go up, but how much it goes up will tell you if rings or valves are the cause of lower compression.