This report has come from SAC (https://support.atlassian.com/browse/STSP-585) but it was originally reported via AAC (https://answers.atlassian.com/questions/104657/source-tree-often-fails-to-commit) with many people reporting the problem. We still never got to the bottom of it as there's no reason it should be happening based on what we know. Escalating it to JAC regardless and hope to provide a consistent reproduction so we can get to the bottom of it.