(Is it just me? ...)

The seventh flute quaver in bar 40 (P26 of "Play Latin", pub Faber) sounds wrong to me, and a G-natural (instead) sounds right. I think this is because of the ensuing E-minor chord in the piano.

Could there be a misprint (ie a missing natural sign before the G)?

When I taught this a couple of years ago, we changed it to a G natural for exactly that reason. I used to sing in an Andrews Sisters tribute group and we sang it as a natural too.

it's one of my faves off the old G5 list. Sad it's not in the new syllabus

Yes, later editions of the music have a G natural. I changed it as soon as it appeared on the old Grade 5 syllabus, and was relieved to find that the CDs, when they came out, also had G natural.