Error: Appearance mismatch may occur when overlapping grouped objects are exported as JPG.

Error: The file was exported but one or more problems were detected: Appearance mismatch may occur when overlapping grouped objects are exported as JPG. Try exporting them as PNG.

I saw this error discussed in another post, but the answers were not relevant to my problem, so I'm starting a new thread.

I have 3 buttons that each turn on/off 3 separate sets of objects that all overlap. Button #2 and it's objects function perfectly. Buttons #1 & #3 cycle through what appears to be missing links (icon of the blue box with ?). All links are updated.

In the epub preview, all 3 buttons and their respective objects function perfectly. But when I export to epub 3.0, I get the error message above, and the missing link icons.

When I do export as PNG, the error message goes away, but the problem with buttons #1 & #3 remains.

The objects that are displaying as missing are the same file format as the objects that work perfectly for button #2, BMP files. They're also on the same layer. I'm viewing the epub in iBooks.

Any help would be greatly appreciated. I can share the file.

Link to file:
https://www.dropbox.com/sh/zo5rnv9yfxx47qm/AACXpzkaLmXQskptF0w6imR2a?dl=0

Dropbox - Problem page Folder

In file: Buttons #1 & #3 ("Pitting" & "Corrosion") trigger the orange +magnifier button to display the missing links.

Button #2 ("Cracking") triggers the orange +magnifier to display the 3 images properly.

Thanks!