Spent a whole Sunday last summer convinced my leak was the water line, so I wrapped it in tape like some kind of plumbing genius and called it fixed. It kept dripping, of course, because the crack was hiding in the overflow fitting just like yours. What finally gave it away was leaving the pump off and filling the pan by hand, then watching a tiny wet line crawl out from a spot I had stared at ten times already. A five dollar part and five minutes of work beat two weekends of me playing detective. Those hairline cracks are sneaky because they only show up when water sits still long enough to find them.

Man that's the exact same thing I saw with my dad's old Pentax after a CLA last year. Honestly the difference was so big I checked the serial number twice to make sure they didn't swap the body on me. If your shutter speeds and focus ring were both gummed up, that alone will wreck your sharpness way more than people expect.