Has the buzzer improved? Maybe it's still not dry with IPA trapped inside? Maybe direct some air to the hole?
If not improved, you could probably get a replacement from digikey/mouser. I don't know the part number or specs, but you could probably find the right parameters using a scope?
No, it hasn't.
I tried applying heat, blowing air, bumping it on the sides, then on the top and bottom, but there was no change.
I tested again even now, and it is the same.
One thing I did notice, though, was that, if I let the buzzer sound continuously for 1 minute or so, it would start to become louder.
But, then, if I let it sit half a minute or so and sound the buzzer again, it would go back to a fainter sound.
In the end, I just bought a cheap 5V buzzer off eBay - probably an unknown brand, but I don't think that matters for this kind of component.