Gossip's inbox feed is not 1:1 to what it pulls down from your inbox relay. There is one system that subscribes to your inbox relays and pulls down events. There are other systems that also pull events for different reasons. Then a separate system constructs your inbox feed from all events regardless of how they got pulled down.

So it might be that the event didn't come from your inbox relay, but was pulled for a different reason, but because it tags you it shows up in your inbox.

I'm wondering what you would like me to do:

1. Chase down what other system pulled this event down, and fix related wrong things, or

2. Make gossip such that inbox notifications only show up for events actually pulled from your inbox relays