Hi Monika Lukow - I think this may be related to a bug fix to make sure the workspace contains file related to the time the build was triggered vs the files currently in the workspace.
Can you please get me the console logs from a broken build on 1.10.0 and the same build working on 1.9.7. If you dont want to post them here you can send them in email to sup...@perforce.com for my attention.