Cannot update tmux-fzf-url: Pulling is not possible because you have unmerged files.

[dagadbm]

everytime I try to update this plugin I get this error.

Am I doing something wrong?

[wfxr]

I often encounter similar problems when updating plugins using tpm, and not only for this plugin. You can go into the plugin directory and reset the git repo manually using command like this:

git reset --hard master

If it still doesn't work, remove the plugin directory and re-install it should be ok.