If I recall correctly, the Allen wrench screws would be the ones that you have to turn for manual landing gear retraction. That could be the issue. I had the popping issue and solved it with the maxima fluid. I suspect that what you are experiencing is more than popping, which I don't think causes measurable cylinder retraction, and that you have an internal bypassing seal issue or a loose connection just barely leeching pressure.
I found that most dealership repair centers think that hydraulics are magic and have no idea what to look for...find a good independent.