Hot take: one 1987 Schwinn brakeless fixie taught me more about wheel building than 2 years of YouTube videos
Last Tuesday I spent 6 hours truing a wheel on a late 80s Schwinn World Sport and kept chasing tension instead of reading the rim, so I'd get it close then lose it again every time I hit a tight spoke. An old timer named Dale who runs a co-op in Missoula walked over, flicked the spokes like a guitar, and said my tension was fine but my dish was off by 3mm the whole time. Rebuilt it in 40 minutes after that and it's been dead straight for a week of daily riding. What's the dumbest thing you've spent hours fighting that turned out to be one basic measurement you skipped?