Bug: Submailbox shows message that is not in the main smart mailbox and doesn't match the rules

Just wanted to add some screenshots.
I think the strangest part is that a message shows up in one of the submailboxes but doesn't show up if you click on the smart mailbox itself.

Mailboxes: https://www.dropbox.com/s/avs96vzjk8isjbw/Screenshot%202019-09-05%2...

Submailbox Settings: https://www.dropbox.com/s/mjkg2g2qz3srwp8/Screenshot%202019-09-05%2...

All Mail: https://www.dropbox.com/s/w03s7nbxdwoscfo/Screenshot%202019-09-05%2...

@Benny: If you need anything else let me know and I can email it over directly.

Also, there is a note in Lighthouse saying "Upload Quota Reached. Please notify the account owner."

FYI, I had another message showing up from a different account, same issue.
I think it could be because I archived it not from within the submailbox?
In this case I archived it from a search, went back to the Month submailbox and it was still there even though it showed that it was in the Gmail All Mail folder (not the inbox).

Moving both messages to the Inbox (I used the account specific mailboxes), then Archiving them again fixed the issue on each.

Sorry for all the updates here. I noticed another issue with the submailbox today.
It's the opposite issue though, there is a message which is in the inbox and shows up in the main smart mailbox, but not in the submailbox for this month, even though the date is this month.

In this case, the message has the same subject as another message from the same sender. It was still missing when I disabled threading in the submailbox (and also when I re-enabled threading).

The subjects (from the smart mailbox): https://www.dropbox.com/s/z2fr1uozh787w14/Screenshot%202019-09-09%2...

In the submailbox, only the most recent message shows up.

Moving the message to the archive, then back to the inbox made it start showing up in the submailbox.

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