Is it possible to send notifications across two different apps?

There are two apps, one for the customer and one for the merchant and they have a unified database in which both the apps connect to. I tried sending notification from the merchant app to the customer app; sometimes it works as it sends the notification to the customer app, and sometimes it sends the notification to itself. Sometimes this is possible but sometimes it doesn't work. If it's possible, what workaround should I do?

Also, when I start sending notifications, especially when I send a notification to a user with the token of a device in which the app is not installed to, the token field goes away and I get an error with code 8, as if sending notif clears the token of the userId and what I do is I re-insert the record with the token and then I can send a notification again and then the issue happens again. Sometimes even just plain sending takes the token field away and there are no logs that may tell what happened. This is intermittent as it happens almost always. @raix

No file, test, or entry point is named in the report; begin by reproducing both the cross-app delivery and token-removal cases with the reported error code 8. Done means establishing whether cross-app delivery is supported and identifying the cause of intermittent self-delivery or token loss.

Written by the indexing model from the issue text.