I do see this part of the execmgr.log at the time of clicking Install for my OSD:
OnOptionalExecutionRequests attempted for package IVP00330 optional program * [QueueRequest: false RunOnCompletion : true QuietMode: true SDKCallerId: (null)] execmgr 10/17/2016 9:36:08 AM 496 (0x01F0)
Validating package IVP00330 program * in the chain. The content request ID is {00000000-0000-0000-0000-000000000000} execmgr 10/17/2016 9:36:08 AM 496 (0x01F0)
Creating an optional execution request for package IVP00330 program * execmgr 10/17/2016 9:36:08 AM 496 (0x01F0)
Content is not available on the DP for this program. The program cannot be run now. execmgr 10/17/2016 9:36:10 AM 496 (0x01F0)
OnOptionalExecutionRequests failed for program * : 0x87d01106 execmgr 10/17/2016 9:36:10 AM 496 (0x01F0)
OR
OnOptionalExecutionRequests attempted for package IVP002B9 optional program * [QueueRequest: false RunOnCompletion : true QuietMode: true SDKCallerId: (null)] execmgr 10/17/2016 9:42:07 AM 3908 (0x0F44)
Validating package IVP002B9 program * in the chain. The content request ID is {00000000-0000-0000-0000-000000000000} execmgr 10/17/2016 9:42:07 AM 3908 (0x0F44)
Creating an optional execution request for package IVP002B9 program * execmgr 10/17/2016 9:42:07 AM 3908 (0x0F44)
Content is not available on the DP for this program. The program cannot be run now. execmgr 10/17/2016 9:42:09 AM 3908 (0x0F44)
OnOptionalExecutionRequests failed for program * : 0x87d01106 execmgr 10/17/2016 9:42:09 AM 3908 (0x0F44)
I have validated that the DPs for this client had all the packages that are part of this Task Sequence (which is ID: IVP00330 or IVP002B9, two different tests seen here). I have tested this same Task Sequence with an older SCCM client and the image works. It seems like I cannot install my Windows 10 Task Sequence or Windows 7 while using client 5.00.8412.1307. If I PXE or Media boot the computer, I can image with no issues.