fourseasons

We have been using OSD task sequences in SCCM 2012 for a few months without issue, recently however the task sequences will fail at the start. From logs, there is not enough free space to copy down the boot image as HD is full of partitions already evidently. I understand that if all packages in the task sequence have the checkbox enabled for "Copy the content in this package to a package share..." we would then get the option in the task sequence deployment to run content from DP rather than download locally, however this has never been set on our deployment(s) and we haven't had this issue before. I believe it should be able to PXE boot to the boot image (which clearly it is already doing prior to starting the task sequence), and for some reason something has changed which means it is trying to copy this locally and hence falling over. For the moment, we can run diskpart from f8 within the task sequence prior to commencing and remove existing partitions, at which point the OSD will complete successfully. Clearly, this would cause issues if we were doing user state migration, which we would like to deploy soon. Any ideas on where to start diagnosing this? I've had no luck tracking down what has changed to alter the behaviour.