OW frame rate drops when getting a message

I recently noticed that I get Overwatch FPS drops when receiving a message in the background while playing the game. It drops the frame rate to more or less an unplayable state (feels like 20-30 fps on a 144hz monitor) and won´t go back up until I read the message and it doesn´t show as unread anymore.

I´m playing in windowed mode on a 144hz monitor with every setting on low except texture details, which is on high.

I don´t know if it is relevant to say that I start OW directly through the overwatch.exe while being logged in into a second account through battle.net, so the messages do not come in on the same account as I play Overwatch on.

EDIT: It also happens in the old client, exact same thing, so I don‘t know if the post belongs here anymore.