We're really sorry to hear about this issue. I've not seen this before. Could you send the following details please?
1. The SSMS version and SQL Server version you are using
2. The Source control software you are connected to e.g. tfs, svn etc
3. Elaborate on the changes that you want to undo; which SQL Server objects are you editing? if you cannot say explicitly what the changes are please give us as much indication as you can.
We sometimes encounter an issue with the Commit tab not updating correctly which we are currently working on (internal ref: SOC_59) but a hard refresh using the refresh button on the Commit tab normally resolves this as does a restart of SSMS.
Thanks for taking the time to notify us of the issue; we'll investigate the issue when we receive more information from you.
Test Engineer SQL Source Control