…a single loosened spoke will generate a broad “S” bend in the rim, a sort of sine wave. If you try and correct this by truing each section of the wave, rather than discovering the true culprit, you’ll have wasted time and possibly worsened the wheel’s condition. Eventually, of course, you’ll find the culprit. Your measure as a builder is how quickly you can find the source of a wheel’s trouble and make a bulls eye correction.
Never spot true.
The difference between those that can form quick and accurate mental maps of wheel tension and those who can’t is huge. It’s like night and day. I pity builders who are essentially blind in their work, stumbling around, superstitious, expecting weird outcomes and struggles. Don’t be among them.
Eventually, you’ll deduce and fix wheels in a fraction of the time it takes others.