That doesn't look like pure Teflon. Not in color, not in chip form. But if this is some kind of Teflon composition, I'll point out one thing I noticed. You're wearing a T-shirt in the first shot, a sweater in the second. Could it be that later on you had a workshop temperature of under 20 degrees Celsius? Teflon should not be machined below the recrystallization temperature (somewhere between 20 and 23 degrees) when it changes dimensions and the workpiece would then be inaccurate or deformed.