We have a MS Teams bot set up in a customer's tenant. The bot is installed in one team. We use the Microsoft Bot Framework REST API & webhooks to receive messaging events from users to the bot, and make API requests to send messages to them.

We noticed today that one user sent us a message with an unexpected tenant ID. The tenant ID of the customer is X and we received a tenant ID of Y in the request body when the user messaged the bot.

We also noticed that the User ID did not match the User we find when listing Users in the one team the bot is installed. The Microsoft Graph object ID is not correct either. Finally, we noticed that the User is marked as a guest account when we look at their profile in the list of Users in the team where the bot is installed.

Why is this happening and how can it be resolved?