Why does the bass play major third in a minor bluesy jazz?

I'm trying to figure out the chords in "The Work Song" by William Clarke from the album Serious Intentions. Until 1:05 the head is played consisting of 16 bars repeated twice. Then the improvisation part with solos is played, it consists of a 12 bar blues repeated while the musicians play their solos. I am trying to figure out the chords in that part. It's clear that the overall key is D minor. However, during at least the first 4 bars of the solos part, at 1:05 through 1:12, the bassist plays

What's up with that F#? Why is it a major third rather than a minor third? Also, it's slightly out of tune. Not in the sense that it sounds bad but in the sense that if I play it on my bass, it's a little out of tune with the recording. Just that one note. Discogs says that the bassist on this recording was Willie Brinlee on "acoustic bass". Does that mean double bass? Also, given that the bass plays F# but the other instruments play F (if they play any third) and the overall key is minor, how should the chord notated? D7? Dm7? D7#9?