I hear it like this, could be wrong, but fits the melody
[DbMaj7---][Ab/C---][BMaj7---][Gb/Ab---] (Ab13sus4)
[DbMaj7---][Ab/C---][BMaj7---][Gbmin7-Gb/Ab-]
[Dbmin7---][BMaj7---][Gb/Ab---][----]
[Ebmin7-Fmin7][Bbmin7---] (chorus)
Its the bass player that makes those bars sound confusing, you're right though, that one measure is tough to get, great song!
Thats all I have time for Happy independence day!