When asking for help I'd not at the same time nag about how things are not "stable", it gives a rather demanding tone for someone asking for help. 

If you are using git, even when checking out a stable branch, small mistakes are to be expected. Most likely full QA will not be run on every commit, but at some specific points in time, like before making a new release out of that branch. Also the issue could very well be due to your specific build environment.

Anyhow, all you have to do to go back 1 commit is:

# git reset --hard HEAD~1

Change 1 for any number of commits you want to go back.

You could also checkout a specific commit:

# git checkout <commit-hash-id>

I personally prefer the former as doing git checkout leaves you in a detached state (unless you create a new branch out of that commit)