Inconsistent oil level N62 4.4 engine

[Doru]

Since I purchased this SAV, I experienced an inconsistent oil level. here is the scoop:
I do an oil change, check the level, everything is OK. A few days later, check the oil level, the level is at the minimum. I add 1/2 qt - the level is now in the middle. A few days later, check the oil level - the level is above the max mark on the dipstick. I leave as is. Then, over a few days, I check the oil level, now it's consistent above the max mark. Then after a few other days, more oil level checks, the level is at min. I don't do nothing, the level is consistent low for a few days. Days later, the oil level is again a smidge above the max level on the dipstick. I am not sure what is causing this. Talked to my friend Fmugur, and also checked the net for answers, and what I can think of are one of 2 issues (maybe both wrong?):

1. Maybe some sludge somewhere, which would not allow the oil to flow freely, and gets pooled somewhere above the oil sump?
2. Faulty Oil Check Valve (p/n 11367539857) part #8 in the below diagram

In realoem there are reported 6 of those, but I am not sure where they are located. The vid below shows the part, and he mentions they are 3 / cylinder head? Any heads up would be really appreciated (DIY? how hard? accessible? need to lift the engine?:

N62 BMW V8 Oil pressure light coming on 745Li 750Li 545i 550i - YouTube