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.

tx.GetHash().ToString(),
                mempool.size(), mempool.DynamicMemoryUsage() / 1000);
            
            set<NodeId> setMisbehaving;
            while (!vWorkQueue.empty()) {
                auto itByPrev = mapOrphanTransactionsByPrev.find(vWorkQueue.front());
                vWorkQueue.pop_front();
                if (itByPrev == mapOrphanTransactionsByPrev.end())
                    continue;
                for (auto mi = itByPrev->second.begin();
                     mi != itByPrev->second.end();
                     ++mi)
                {
                    const CTransaction& orphanTx = (*mi)->second.tx;
                    const uint256& orphanHash = orphanTx.GetHash();
                    NodeId fromPeer = (*mi)->second.fromPeer;
                    bool fMissingInputs2 = false;
                    
                    
                    
                    CValidationState stateDummy;
                    if (setMisbehaving.count(fromPeer))
                        continue;
                    if (AcceptToMemoryPool(mempool, stateDummy, orphanTx, true, &fMissingInputs2)) {
                        LogPrint("mempool", "   accepted orphan tx %s\n", orphanHash.ToString());
                        RelayTransaction(orphanTx);
                        for (unsigned int i = 0; i < orphanTx.vout.size(); i++) {
                            vWorkQueue.emplace_back(orphanHash, i);
                        }
                        vEraseQueue.push_back(orphanHash);