Check the quick release first every single time, no joke. Takes ten seconds and costs nothing, so why would you save it for last? Pulling cranks and chasing bottom bracket gremlins before you've even checked the wheel is just backwards, and you burned 6 hours proving it. The wheel is literally the easiest thing on the whole bike to check and loose dropouts cause way more clicks than people want to admit. I get that a BB click feels more likely, but bikes don't care about what feels likely, they care about what's actually loose. Start at the axle and work inward, and you'll never waste another afternoon like that again.