One factor that the Wells report ignores is the amount of time that passed between measuring the Pats footballs vs. the Colts. This is an important factor because the pressure returns very quickly. I read about an experiment that was done back in January about balls taken from a 70 degree room to a 40 degree temperature outside and the balls dropped 1.5 psi as expected. But after just 15 minutes in the 70 degree room, the psi had adjusted back.
We know the Patriots footballs were measure first and only 4 Colts balls were measured as they ran out of time. We also know the officials locker room was just over 70 degrees. So, if the Patriots footballs were measured on average of just 5 minutes or so earlier, that could explain the entire difference between each team's footballs.
Edit: Upon reading further, I see that the Exponent report does address this and determines that it does not account for the full difference. The problem I have with this is that this determination assumes they have perfect information to the times each team's balls were measured. By their own calculations if the time disparity is just two minutes longer than their assumptions, then their calculations would account for the entire difference between the two sets of balls. Just two minutes of an estimated timeframe provided by the referees would change their conclusion entirely.