Why does Gmail app keep hiding stuff in my inbox, primary tab??

[The19thD0CT0R]

I keep having an issue where what is on my android gmail app (stock android M, nexus 6) does not reflect exactly what is there if I go to gmail on the web. Right now, I have four emails in my primary; the oldest is from 7/28/16, it is starred and "important". I have in my settings the "days of mail to sync" set to 999 days, and in the labels almost everything is synced to "all". Yet, often, that last email will be hidden, and I have to go to "all mail" to find it, even though it is still labeled "inbox". How can I get this to never hide emails and show exactly in every label what is there on the web client? On a side note, when I set the label of "all mail" to sync all, everything disappeared; when I set it back to none, everything showed under that label again. Do I have conflicting sync settings that is causing the older email to be hidden? What is the optimum settings to have your mobile app reflect what you have on the web gmail? Thanks for any suggestions and advice!