in v0.12 https://github.com/bitcoin/bitcoin/pull/7081 (by @luke-jr) was merged adding `-bytespersigop` (with default of 20).

this is preventing simple bare multisig transactions from being accepted into mempool when the size is < 400 bytes.  
eg; https://gist.github.com/rubensayshi/ac4f617207f7a50559e85d61c05800be

from 1-of-7 and onwards they are accepted because the ratio of bytes:sigops is high enough.  
also having 2 or more inputs will work because it again tips the ratio of bytes:sigops over.

the reason mainly being that `GetLegacySigOpCount` calls `GetSigOpCount` with `fAccurate=false`.

It looks like changing `GetLegacySigOpCount` to use `fAccurate=true` would cause side effects in the few other places (`ConnectBlock`, `CheckBlock`, `CreateNewBlock`) and simply adding `fAccurate` as arg to `GetLegacySigOpCount` would affect the value stored in `CTxMemPoolEntry.sigOpCount` which in turn affects a bunch of other things.

nLocalServices = ServiceFlags(nLocalServices | NODE_WITNESS);
        
        
        nRelevantServices = ServiceFlags(nRelevantServices | NODE_WITNESS);
    }
    
    if (mapArgs.count("-blocknotify"))
        uiInterface.NotifyBlockTip.connect(BlockNotifyCallback);
    std::vector<boost::filesystem::path> vImportFiles;
    if (mapArgs.count("-loadblock"))
    {
        BOOST_FOREACH(const std::string& strFile, mapMultiArgs["-loadblock"])
            vImportFiles.push_back(strFile);
    }
    threadGroup.create_thread(boost::bind(&ThreadImport, vImportFiles));
    
    bool fHaveGenesis = false;
    while (!fHaveGenesis && !fRequestShutdown) {
        {
            LOCK(cs_main);
            fHaveGenesis = (chainActive.Tip() != NULL);
        }
        if (!fHaveGenesis) {
            MilliSleep(10);
        }
    }