I have replaced the adjuster one year ago, along with the magnet and the chain tensioner. Seen and fixed the oil leak you mentioned, too.
The problem that I did not install it right first time when I done the replacement. The adjuster consists of several parts that slide one into each other...long story short, I did not slide them in all the way. I got lucky (or so I thought) - the only problem I've experienced was the check engine light because the magnet could not pull the adjuster core anymore. I reassembled and reinstalled everything, the light was gone, and I assumed that the incident is resolved. But maybe the adjuster experienced some premature wear because of this.. have no clue. Maybe it is not the adjuster at all.
Anyway, anything you'd suggest me to pay attention when I take the cover off? In particular I'm interested if I can (or need) to check the tension of the timing chain.

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2002 C230K