Ambiguous 8va in Outdoor Overture

[AtomicClock]

In Copland's Outdoor Overture, the trombone 1 part occasionally is written 8va. In this instance (bar 239):

the 8va is written over fifth-line A. But according to the score, the part is not octave-shifted until a beat later:


Do we read 8va as indicating the note underneath, or the note(s) to the right? Or is this just sloppy typesetting?

[AtomicClock]

It's correct in the 2nd part:

[robcat2075]

As a general rule, the score is always right... until it isn't.