Curious how you set your baseline before you even trust the chart, like do you pick a fixed point on the turntable or pads and measure off that every time? Our old timer used to make us check the same spot twice with two different tapes, and if they didn't match within a quarter inch we stopped and figured out why. Bet a bent hook bites a lot of guys because the tape still looks fine till you lay it flat on a bench. What's your go to when the tape and the chart still won't line up after a second check?

Leave yourself a couple pounds of buffer, since those airport scales can be off a bit either way. I weigh my bag at home and just assume it's a pound or two heavier than my scale says, so I aim to land around 38 on mine (which sounds like exactly what you did). Be a little strict on the way out and you won't get surprised at the counter.