public synchronized void registerFailedGetBlock(
        final long blockNumber, final Optional<Hash> maybeBlockHash) {
      requestedNonAnnouncedBlocks.remove(blockNumber);
      maybeBlockHash.ifPresent(requestedBlocks::remove);
    }
Try to request the lowest ancestor for the given pending block or process the descendants if
the ancestor is already in the chain
ethereum/eth/src/main/java/org/hyperledger/besu/ethereum/eth/sync/BlockPropagationManager.java