Pointing at clear sky and adjusting the parallax knob, the reticule was sharp 90% of the time
I think you are going about it wrong. If your scope has a focus ( parallax ) adjustment on the side, leave it alone for now.
The first thing is to get the crosshair in focus. This needs to be done carefully so that it is nice and sharp the moment you mount the rifle.
The easiest way I know to do it is to take the eyepiece. . .not the focus knob ( parallax ), and turn it clock wise all the way in until the crosshair is well blurred.
After you have done that, aim the scope at a neutral background. An off white wall or a berm at the range will work also.
Begin turning the eyepiece counter clockwise until the cross hair starts becoming clear. As you get close, take your eye off the scope. This will prevent or minimize what we call "accommodation." Accommodation is what occurs when your eye tries to make something that is a little out of focus to be in focus and contributes to eyestrain.
Look through the scope again and continue to turn the eyepiece counter clockwise until the image is sharp when you first look through it. Half turns of the adjustment are normal here until the crosshair is clear and crisp at the moment you look through the scope. It may take a little trial and error of moving too far and having to start all over. That is ok. The goal is to get the crosshair clear first.
Once you are satisfied, lock the lock ring and leave it alone. If you wear corrective lenses, make your adjustment with them on. . .UNLESS you shoot without glasses. For many years that is what I did. At the range I frequent, you MUST have glasses on all the time.
If you shoot with regular shooting glasses ( no correction ) it makes no difference.
Now that you have the cross hair focused, look through the scope at the target you want to shoot.
Select your magnification if you have a variable and set your focus knob ( parallax ) adjustment to infinity and then bring it back until the target is clear.
If you move your eye slightly side to side or up and down, you should see NO relative movement between the target and the cross hair.
If you DO see movement, parallax is present and should be corrected out by further manipulation of the focus ( parallax ) knob.
This MIGHT mean a slight degradation of the target definition.
For hunting purposes, you will have to wing it. You will have to generalize a lot to make the shot and you will not have time to tweak any adjustments.
For target shooting, you generally have all the time in the world to get things set.
One thing to remember though. . .once the crosshairs are in focus for YOU, you should leave it alone unless you are changing from shooting with glasses to shooting without them.
When I used to hunt groundhogs, I wore glasses so I could look for movement around the edges of the fields. When I saw movement. . .off came the glasses and up came the binoculars. My binoculars and rifle scope were all adjusted for me to see clearly without my glasses. Anyone else using my rifle would have a problem.
If you wear glasses and your vision is 20/20 corrected with glasses and you use those glasses to set up your rifle, anyone with 20/20 uncorrected vision should be able to pick up your rifle and do pretty well with it as long as the rifle fit them like it fits you.
Sorry this is so long and hope it helps.