While backward processing the log, the length of the next block does not match the data control block (DCB) information, or the last two bytes of the block descriptor word (BDW) are not zero.
Dump the log using a utility such as DWWJUP. Examine the faulty block, correct it, and rerun CICS VR.
For information about the CICS® DWWJUP utility, see PRINT: print information about records logged on an MVS log.