Any air in the cylinder will eventually work it self out. Air will make it feel spongy, but after awhile, should go away. As far as the bucket and BH dropping, that is also normal. You say you changed fluid, are you using a fluid with the right viscosity. If you went thinner, it might drop faster. Selector valve could be leaking.
You have to remember, that if the bucket and or BH is left up and engine is shut down, The cylinders will be in a ram mode, the weight and length of the metal is trying to compress the fluid, and they will leak down, and you will not see any fluid.
Cylinders have o-rings and seals that can help seal the cylinders, but the valve, at least most of them have no o-rings, and rely on the tolerance of the manufacture to specify valve leakage. As the valves with out o-rings get worn, they will leak more, until you have to replace the valve. O-ring valves can be rebuilt, almost good as new.
You can determine the leakage by observing the fluid from the out hose on any valve setup. Most people are not willing to do this, but if you installed a tee, and a needle or gate valve in the out fitting of the valve, you will have a test port. Here is how you would test. With the needle valve open, and a cap still on the tee, raise the FEL up, and shut off the engine. Remove the cap off the tee and put a hose on it and place in a clean 5 gal container. Close off the gate or needle valve. You can figure the volume that a hyd cylinder contains, and if the valve is leaking, then you should see that fluid in the container.
Some manufactures rate their valves by drops by minute, cc's/oz's by hour, etc.
Don't hold your breath, hoping the dealer will replace that new valve, because the bucket or the BH descends over night. If you can convince him it is excessive, and stay on him, he might replace it.
If you have the assets and time, you can take the valve off and take it to a good hydraulic shop, and tell them to test for pressure, relief pressure, and the leakage rate.
