I'd say each individual part comes across really well! Really well indeed! So from that standpoint, it's pretty well mixed. Nice job.
You are shooting for a swing waltz feel, and occassionally it all rides together nicely. But I'd do a little more work in making sure everything follows the drums. They are riding a little behind the beat, as they should. But the piano in particular seems to be right on the beat, or is quantized which seems to eliminate any "swing" . . .
I'd let the drums be your timing guide, I'd slip the piano back in time in a whole bunch of different spots. Your timing issues all manifest themselves when everyone is playing together.
I don't know how you mixed this, but I'd start with bass and drums only, get them swingin' together, then add flute and piano one at a time.
It is beyond doubt a really lovely piece, so compositionally, bravo!
cheers,
-Tom