: I used MIXOL tints from Woodcraft
: (http://www.woodcraft.com/family/2005522/mixol-universal-tints.aspx)
: which isn't supposed to impact the adhesion. I did wait several
: weeks between the initial non-tinted coats and the two tinted
: coats -- that may have been my mistake.

Yeah, that's the issue, especially if you didn't sand before applying the final coats. Chances are that if you had done the last two coats at the same time as the initial coats, you wouldn't have had an adhesion problem.