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.

if (!pfrom->fInbound) {
            LogPrint("net", "Ignoring \"getaddr\" from outbound connection. peer=%d\n", pfrom->id);
            return true;
        }
        
        
        if (pfrom->fSentAddr) {
            LogPrint("net", "Ignoring repeated \"getaddr\". peer=%d\n", pfrom->id);
            return true;
        }
        pfrom->fSentAddr = true;
        pfrom->vAddrToSend.clear();
        vector<CAddress> vAddr = addrman.GetAddr();
        BOOST_FOREACH(const CAddress &addr, vAddr)
            pfrom->PushAddress(addr);
    }
    else if (strCommand == NetMsgType::MEMPOOL)
    {
        if (!(nLocalServices & NODE_BLOOM) && !pfrom->fWhitelisted)
        {
            LogPrint("net", "mempool request with bloom filters disabled, disconnect peer=%d\n", pfrom->GetId());
            pfrom->fDisconnect = true;
            return true;
        }
        if (CNode::OutboundTargetReached(false) && !pfrom->fWhitelisted)
        {
            LogPrint("net", "mempool request with bandwidth limit reached, disconnect peer=%d\n", pfrom->GetId());
            pfrom->fDisconnect = true;