I'm unsure whether this is a Sway specific issue, however I did not encounter
it on KDE Plasma (both X11 and Wayland).
If I copy something in an application, and then paste it, the clipboard will
sometimes return the _previous_ thing I copied. This does not happen always,
but a lot of times between various different applications (Alacritty, Firefox,
Slack, ..).
With `wl-copy` and `wl-paste` the issue is not reproducible - `wl-paste` always
returns the last thing entered in `wl-copy`.
For debugging I enabled `clipman` in Sway. With it I found that all my copies
in applications (with their respective Ctrl+C or Ctrl+Shift+C shortcut) show up
in `clipman --show-history` correctly, even if a following paste attempt (with
the respective Ctrl+V or Ctrl+Shift+V) might return the _previous_ entry.

Would appreciate any ideas.