Reported here https://github.com/bitcoin/bitcoin/pull/12629#issuecomment-381095603 by @Empact.  I've seen it now in a few different travis jobs, including:

https://travis-ci.org/bitcoin/bitcoin/jobs/366157920
https://travis-ci.org/bitcoin/bitcoin/jobs/366139851

From my initial investigation it seems like there may be an actual bug in block announcement, so I'm  opening this issue to track.
return g_chainstate.PreciousBlock(state, params, pindex);
}
bool CChainState::InvalidateBlock(CValidationState& state, const CChainParams& chainparams, CBlockIndex *pindex)
{
    AssertLockHeld(cs_main);
    
    
    
    
    
    bool pindex_was_in_chain = false;
    CBlockIndex *invalid_walk_tip = chainActive.Tip();
    DisconnectedBlockTransactions disconnectpool;
    while (chainActive.Contains(pindex)) {
        pindex_was_in_chain = true;
        
        
        if (!DisconnectTip(state, chainparams, &disconnectpool)) {
            
            
            UpdateMempoolForReorg(disconnectpool, false);
            return false;
        }
    }
    
    
    while (pindex_was_in_chain && invalid_walk_tip != pindex) {
        invalid_walk_tip->nStatus |= BLOCK_FAILED_CHILD;
        setDirtyBlockIndex.insert(invalid_walk_tip);
        setBlockIndexCandidates.erase(invalid_walk_tip);