The issue was first uncovered by errors during OSD deployments, failing with 80040104 on the Client Package ID:
I tracked this down to content on the CAS, and subsequently all DPs containing invalid packages, inside cd.latest\smssetup\client\i386 and x64 folders containing files with 0 kb in size:
Super frustrating. And then confirmed by finding these "WARNING: File hash mismatch for" under CMUpdate.log which didn't bother to flag any errors:
Has anyone ever run into this type of issue before? Is there an easy way to force a redownload and a reapply of the update that would have contained this content?