Some instruments don't work - e.g. Oboe

I have a MIDI file which contains scoring for several orchestral instruments, including Oboe.

I want to play the file in GarageBand.

When I attempt to do so, it plays most of the instruments correctly, but the Oboe comes out sounding like a Clarinet.

Sure enough, in the track list, the instrument is listed as a 'Clarinet Solo', despite it having been encoded in the MIDI file as an Oboe.

Just to be sure, I tested the same MIDI file in a separate application, MuseScore, and that application correctly produces an Oboe-like sound for the Oboe line.

I tried changing the instrument to an Oboe by right-clicking on the image of the instrument, then selecting the 'Percussion' tab, then clicking the image of the Timpani. When I did this, the icon of the instrument changed. But when I tried to play the file again, the instrument still seemed to sound like a Clarinet, as if I'd done nothing at all.

I'm pretty sure it's not my hearing that's the problem; a Timpani should sound drastically different to a Clarinet or an Oboe.

I'm not sure why these instruments aren't working.

I've had a window pop up several times before asking if I wanted to download some kind of additional sound library. I clicked Yes and allowed it to download all 2 GB, which failed several times before it finally succeeded and installed.

But that massive update doesn't seem to have improved things, as I'm still finding that most instruments, including the ones above, still don't work.

Is there any way to actually install the sounds for these instruments and get them working?

If I have to pay to download some kind of sound addition, I don't mind, as long as I can be sure it will actually work.

Any help would be greatly appreciated. Thanks.