Urbestfriend changes oil usually every 1,000 miles. This is around 6 or 7 times on either of my 2 bikes. I always drain thru the side drain plug and then disassemble, drain and clean the bottom screen.
Today when screwing and tightening the bottom cover back on, the flange that the 30.8mm o-ring sets in cracked and separated clean off. The plug and o-ring are in place, but I will not add oil until replacements are delivered. As you know, unless your dealer is special, replacement parts are not readily available.
This cap appears to be a molded powdered metal product evidenced by the rough surfice in the fractured area.
Some would say, "Don't overtighten it" and can't say that I have. Just the repeated stesses will always get
you after a while.
I always recommend spending $100-200 dollars on items that are prone for replacement. O-rings, drain plugs,
brake pads, oil filters, etc. I just hate to drive my car.