Here is the relevant error message from the debug file:

Opening LevelDB in C:\Users\home\AppData\Roaming\Signatum\txleveldb
Transaction index version is 70510
Opened LevelDB successfully
LoadBlockIndex(): hashBestChain=bb2bb761740ba517035ef6f40ec45020d57d6632f5a7983a6f2bdc9a77f01580  height=19282  trust=503842449171527692  date=08/01/17 02:55:37
Verifying last 500 blocks at level 1
ERROR: CheckProofOfWork() : nBits below minimum work
ERROR: CBlock::ReadFromDisk() : errors in block header
ERROR: LoadBlockIndex() : block.ReadFromDisk failed