Combobox dropdown height cut off on mac only. Scollbar doesn't render.

I've built a PDF form where selecting one dropdown decides which items show in another dropdown. In Acrobat on mac only, the second dropdown is sometimes cutting off list items at the bottom and there's no scrollbar. Heads-up, I've already tried touchmode -- always.

So combobox 1 contains:

[

  [red, 1],

  [orange, 2],

  [blue, 3]

]

combobox 2:

if combobox1 selects red:

[

  [straberries, 1],

  [firetrucks, 2],

  [apples, 3],

  ... more items

]

if combobox1 selects orange:

[

  [oranges, 1],

  [fire, 2],

  [more oranges, 3],

  ... more items

]

And so on.

for some reason, if I select red in combobox1, combobox2 has a scrollbar and all elements can be viewed. If I select orange or blue in combobox1, combobox2 cuts off its last item and does not have a scrollbar. This occurs only in Acrobat on a mac.

I've tried this a couple ways:

1) combobox1 toggles through display visibility on a collection of comboboxes for orange, blue, etc.

2) combobox2 is populated from a document-level array based on combobox1 selection.

In both cases, the same thing happens. Still, only on a mac.

If anyone knows what's going on with this, I'd love the help. Thanks!