I'm having a very strange issue. Chat notifications from a single contact disappear on my Galaxy S10+ almost immediately after they show up. It's acting as though I have another device open with a chat session window open with the same contact. To rule this out, in addition to checking all my devices, I also changed my password. I also have 2fa in place. Chats from other contacts (both external and internal) and channels are all showing up fine. The contact is another internal user. I have no idea what the hell is going on I'm hoping someone else has come across this before reaching out to MS support.
Also, I have checked any 3rd party apps that might be causing issues and haven't found any.