powerlevel10k: Instant prompt output error only in tmux

Hi, first of all, thanks for this amazing prompt! I recently started using tmux and I noticed something weird. When I start tmux, even with no config and no plugins, I get this error:

[WARNING]: Console output during zsh initialization detected. Then long instructions follow and at the end, this:

-- console output produced during zsh initialization follows --

╭─░▒▓    ~ ············································································································· ✔  23:04:09  ▓▒░
╰─

There’s just one newline, but I don’t know if that is part of the error or the console output.

This happens only in tmux and when I run exec zsh or zsh after that, no error occurs. When I create a new tmux window or pane, new error happens there. Sometimes, it doesn’t happen when I start tmux but alway when I create new window or pane.

At first, I thought it’s caused by some of my tmux plugins, but it happens even with the default tmux config on my pc. On my Android phone with Termux, it doesn’t happen, even though I have the same dotfiles here. It cannot be caused by my terminal, it happens in konsole and wezterm.

Thank you for any help or at least pointing me to where can this error come from.