Mac Designer: moving artboard vanishes other artboard's symbol instances!?

[VectorCat]

I have a document with 9 artboards. One of them I dragged off to the side for later. the other 8 each has instances of a symbol on them.

when I move artboard 9, the symbol instances on the other 8 artboards disappear!  artboard 9 doesn't have this symbol on it. Same result if I delete artboard 9.

why does artboard 9 have apparent existential sway over the symbols on other artboards?

thank you for any clues!

 

Edit:  trying to put another instance of the symbol from the symbol panel onto an artboard with nothing on it, and just doing that made the other symbol instances disappear. 

Edit #2: in working with this same document, I am seeing a fair amount of disappearing symbols. Anyone else experiencing similar with their symbols?

Bug?

[Lee D]

Symbols can be a little funny sometimes in how they are setup. Would you be able to upload a copy of your file here or if private send me a link via DM so I can take a look and if needed I can log any issues for the developers to take a look at.

[VectorCat]

22 minutes ago, Lee D said:

Symbols can be a little funny sometimes in how they are setup. Would you be able to upload a copy of your file here or if private send me a link via DM so I can take a look and if needed I can log any issues for the developers to take a look at.

Quite possible for me to provide you with something, yes. The document in which I noticed this is proprietary, but easy enough to create something comparable simply to demonstrate what I’ve seen. I appreciate your looking it over.