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Not sure why the covers rotated, but there's nothing tune related or internal to the vanos assembly that would cause it. The cap clips to the outer ring of the rotor housing, nothing else touches it. I suspect someone may have been in there previously who messed with them. There are rotors inside the vanos that limit the rotation of the vanos internals and the attached cam. If those rotors become damaged then you'll hear lots of strange clacking. That won't cause the cap to rotate and you'll often end up with vanos codes causing a check engine light, but not always.
I say replace them and move on. Used ones can be purchased, however be very careful to buy them from a honest and reputable seller who can guarantee them as these engines are usually only dismantled due to bearing failures, and you DO NOT want the vanos units from those engines as the bearing material can migrate into the internal rotors and jams their movements. You won't know if the vanos unit is good or not until you fire up the engine and put a few miles on it. You don't want to go through all the work of installing a set of bad adjusters over the temptation to save a few bucks.
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