The service's status page reports that "something's not quite right" with messaging, apps, integrations, and connections. The issues began this morning and are still ongoing. It says that it is looking into it.
One of my co-workers reported that their notifications weren't showing up correctly and that threads would load at random, while another reported that their notifications weren't showing up correctly. The app sometimes hangs when I try to load a channel, and it only lets me scroll back a certain amount, and the app also kicked me out of the Threads screen when I tried to type a reply. The Threads screen was broken completely by another colleague.
These issues are not as work-breaking as a full Slack outage would be. There isn't a lot of chatter about it on social media and there aren't a lot of reports on DownDetector.com. You aren't imagining that things aren't quite right, but you hope that things will get sorted soon.