three dots - missing obb patch file?

I keep getting three dots when I download an update from the store. It happens when the download is a partial update,  not a full reinstall.    I have to uninstall and do a full re-install. 

Looking at adb logcat, I see that it is not finding an obb patch file:

[GameActivity] Checking for file : patch.com.gamecompany.XXXX.obb
UE4 : [GameActivity] which is really being resolved to : /storage/emulated/0/Android/obb/com.gamecompany.XXXX/patch.com.gamecompany.XXXX.obb
UE4 : Or : /storage/emulated/0/obb/com.gamecompany.XXXX/patch.com.gamecompany.XXXX.obb
UE4 : [GameActivity] ... Whoops... missing; go go go download system!

What causes that?  It's true that if I look at Internal Shared Storage/Android/obb/com.gamecompany.XXXX/, I do not see the obb patch file.  I see the main, and the additional overflow obb which is never mentioned in the adb log.