尝试通过源树推送时，出现以下错误：

git -c diff.mnemonicprefix=false -c core.quotepath=false -c credential.helper=sourcetree push -v --tags origin refs/heads/master:refs/heads/master 
Pushing to https://user@github.com/repo.git
To https://user@github.com/repo.git
 = [up to date]      master -> master
...
 ! [rejected]        example_tag -> example_tag (already exists)
updating local tracking ref 'refs/remotes/origin/master'
error: failed to push some refs to 'https://user@github.com/repo.git'
hint: Updates were rejected because the tag already exists in the remote.
Completed with errors, see above

据我所知，我没有对此标签进行任何更改。我怎样才能解决这个问题？