Hi there, thanks for the additional details.
A high Connection Quality Score is definitely useful information, but it doesn't completely rule out connection-related issues, as things like routing, packet loss, or temporary instability can still affect matchmaking or gameplay.
From here, the main thing we can do is provide troubleshooting steps that may help improve the connection and rule out common causes. We don't have the ability to make changes to your connection or matchmaking from our side.
Please try the connection troubleshooting steps here:
https://help.ea.com/en/articles/troubleshoot-connection-issues-eacqr/
Since you've mentioned this only happens in Rivals, if the issue continues after trying those steps, please let us know exactly what happens when you attempt to enter a Rivals match, including any error message you receive.