Now this may sound like an odd question regarding oil leaks, but what brand/weight oil are you using. Since I switched to Chevron DELO 400, my oil fill cap hasn't leaked. Recently though, when I drove to VA, needed to add some oil and used some Castrol, my cap started to leak. It seemed rather odd for it to just start leaking again. For the vent tube, you could try tightening the clamp around the fitting.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
MBCA member