Conversations involving multiple participants, allowing collaboration and information sharing in Teams
Dear Austin,
Baed on your information, the Teams is still having this issue even when you confirmed the settings are fine. I agree that this might be some backend issue, so I did some research about this.
Currently for Teams, there is an SI has been released which is related Teams function for Andriod OS:

Although the detailed issue is not as the same as which you have reported, currently for Teams for Mobiles, there are some other service issues reported, like missing channels in Teams for Mobile. In this situation, I suppose that there are some service issues that are not discovered or not officially released by the product team now.
So, the quickest way to confirm is to ccontact the our higher-level support group: Please go to Office 365 Admin Center-> Support-> New Service Request. The support engineers there have the correct escalation channel, and this is the most efficient way to report such issue. You can refer to this article to check the way how to raise a ticket: Ways to contact support for business products - Admin help. The engineers in related team have higher permission and resources than us, they would provide the detailed information is this issue is caused by the backend problems and would share you the latest work around if threre is any.
At the same time, I will keep collecting and monitoring this issue in our forum and checking with the official notifications. When I get any useful information, I will let you know ASAP.
Meanwhile, if you could get any information after reaching the support group, kindly share the information back here, this would be very helpful for all of our engineers and users in this communnity.
Thanks for your time and your understanding would be highly appreciated.
Sincerely,
Sherry | Microsoft Community Moderator