All chat messages are automatically deleted once there are more than two messages visible. I don’t have any ad blockers installed. 7TV is running with default settings. This issue occurs on both large channels with fast-moving chat and small channels with slow chat. It doesn’t matter whether the messages are in Cyrillic or Latin. Emotes load correctly, but I’m unable to run commands like /refresh, and the emote picker window disappears as well.
In the recorded example, FFZ is also installed, but 7TV emotes are disabled in FFZ to avoid any conflicts. I remember encountering a similar issue in the past when Twitch changed the layout of the video player.