Update: spent 5 hours on a warped cabinet door before I checked my assembly table
I was building a shaker door for a kitchen in Fargo and the gaps were off by almost 1/8 inch on the top rail no matter how many times I recut the joinery. Turned out my assembly table had a low spot right in the middle from years of dropped clamps and lumber, so every door I glued up there was getting a slight twist baked in. A $12 straightedge from the hardware store would have caught it in about 30 seconds. Anyone else find their flat surface was the real problem the whole time?
A low spot of what, like a 16th of an inch? Guys build doors on two sawhorses in a driveway and they come out fine. An 1/8 inch gap sounds more like the rail was cut short or the tenon was sloppy, and the table just got blamed after the fact. Wood moves on its own anyway with the seasons, so a tiny bit of twist in a glue up isn't the end of the world. Five hours though, at some point you gotta stop and look at your setup instead of recutting the same joint over and over. How much was the table actually out, did you put a level on it and measure?