hello good.
From what you comment, I wanted to ask you, you adjusted the rings gap, when riding the pistons in the engine you align the rings according to the manual?
Pressure can be lost by the engine butt, for the cylinder head (do a pond test to verify where you lose pressure), review the valvular train again and verify that the valves are completely closing, that they do not have a game in the adjustment of the seats or of the valve guide, that the springs are in good condition between countless things that can fail.
Finally, I don't know how you perform the engine compression test, but something that I always do when I verify an engine is to open the acceleration body completely, so that the engine aspires as much air as possible. Try it, I get the pressure reading a bit.
I hope I have helped you with the problem, good luck.