Phil has been working on some sync issues for the december hotfix #1

On Dec. 7, testnet B node 4 went out of sync. several attempts to restart it proved problematic as the sync feature continually got out-of-order blocks, or in some cases simply stopped dead.
After log analysis, code review, and localized testing, It was determined that the sync manager object was still requesting concurrent sets of blocks from multiple peers, rather than the intended behavior of receiving one chunk at a time but varying the intended requester so as to avoid excessive burden to a single peer.

275 and this issue are aimed at preventing block producer nodes from hanging or crashing as a result of at least some user error, such as loading the wrong genesis.json file