I get a lot of spurious messages like this in the log:
```
2019-08-31T18:07:53Z Synchronizing blockheaders, height: 592633 (~100.00%)
2019-08-31T18:09:40Z Synchronizing blockheaders, height: 592634 (~100.00%)
2019-08-31T18:09:40Z Synchronizing blockheaders, height: 592634 (~100.00%)
2019-08-31T18:09:40Z Synchronizing blockheaders, height: 592634 (~100.00%)
2019-08-31T18:09:40Z Synchronizing blockheaders, height: 592634 (~100.00%)
2019-08-31T18:09:40Z Synchronizing blockheaders, height: 592634 (~100.00%)
2019-08-31T18:10:28Z Synchronizing blockheaders, height: 592635 (~100.00%)
2019-08-31T18:10:28Z Synchronizing blockheaders, height: 592635 (~100.00%)
2019-08-31T18:10:28Z Synchronizing blockheaders, height: 592635 (~100.00%)
2019-08-31T18:10:28Z Synchronizing blockheaders, height: 592635 (~100.00%)
2019-08-31T18:10:28Z Synchronizing blockheaders, height: 592635 (~100.00%)
2019-08-31T18:11:01Z Synchronizing blockheaders, height: 592636 (~100.00%)
2019-08-31T18:11:01Z Synchronizing blockheaders, height: 592636 (~100.00%)
2019-08-31T18:11:01Z Synchronizing blockheaders, height: 592636 (~100.00%)
2019-08-31T18:11:01Z Synchronizing blockheaders, height: 592636 (~100.00%)
2019-08-31T18:11:01Z Synchronizing blockheaders, height: 592636 (~100.00%)
```
also
```
2019-08-31T18:19:47Z New outbound peer connected: version: 70015, blocks=592636, peer=0
2019-08-31T18:19:47Z Synchronizing blockheaders, height: 592636 (~100.00%)
2019-08-31T18:19:47Z New outbound peer connected: version: 70015, blocks=592636, peer=1
2019-08-31T18:19:48Z Synchronizing blockheaders, height: 592636 (~100.00%)
2019-08-31T18:19:48Z New outbound peer connected: version: 70015, blocks=592636, peer=2
2019-08-31T18:19:49Z Synchronizing blockheaders, height: 592636 (~100.00%)
```
This log message was introduced in #15615 by @jonasschnelli..
From what I understand, it's supposed to only be shown once per 2000 blocks, not multiple times for the same block.


std::set<CBlockIndex*, CBlockIndexWorkComparator>::iterator it = setBlockIndexCandidates.begin();
    while (it != setBlockIndexCandidates.end() && setBlockIndexCandidates.value_comp()(*it, m_chain.Tip())) {
        setBlockIndexCandidates.erase(it++);
    }
    
    assert(!setBlockIndexCandidates.empty());
}
/**
 * Try to make some progress towards making pindexMostWork the active block.
 * pblock is either nullptr or a pointer to a CBlock corresponding to pindexMostWork.
 */
bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace)