I'm knitting away on a lovely green sweater and measure it - check the schematic - measure again - knit some more - measure again - check the schematic. It's not coming out correctly.
So rather than looking for errata I frog the whole thing, in spite of the fact that my gauge swatch was perfect.
This morning I get up and do a bunch of scribbling and decide to check for errata. There it is - a simple measurement missing from the schematic. Drat!
Oh well. Back to knitting.