Sending an email invitation to a user that already has team repo access, and the team is on its user limit, doesn't work

Summary

Assume that you have a team with the maximum number of users that the billing plan allows, e.g. a team on the 5 user plan, with 5 users in it. One of those 5 users has direct repo access only, and doesn't belong to any team user groups.

If you send this user an email invitation to another repo of the team, then the user will see the following when accepting the invite:

That's even though his account already counts towards this team's users.

Steps to Reproduce

1. Create a team in Bitbucket – the team will be by default on free 5 user plan
2. Create two private repos in the team, repoA and repoB
3. Add 3 users to one of your team's User Groups (including yourself, that will be 4 users in total)
4. Afterwards, add a 5th user directly to repoA, from this repo's Settings >> Access Management
5. Then, go to repoB, and open its Overview page
6. At the top right corner of the page, there will be a link to Send Invitation to users:
7. Select that, and in the popup that opens, select the tab Repository
8. Add the 5th user's email (not his username) and then send the invite

Expected Results

The 5th user is able to accept the invitation.

Actual Results

When the 5th user tries to accept the invitation for repoB, he sees this message:

Workaround

Add the user's Bitbucket username directly to the repository's Settings >> Access Management page.