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 (mi->second->nHeight >= chainActive.Height() - 10) {
                            CBlockHeaderAndShortTxIDs cmpctblock(block);
                            pfrom->PushMessageWithFlag(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::CMPCTBLOCK, cmpctblock);
                        } else
                            pfrom->PushMessageWithFlag(SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::BLOCK, block);
                    }
                    
                    if (inv.hash == pfrom->hashContinue)
                    {
                        
                        
                        
                        vector<CInv> vInv;
                        vInv.push_back(CInv(MSG_BLOCK, chainActive.Tip()->GetBlockHash()));
                        pfrom->PushMessage(NetMsgType::INV, vInv);
                        pfrom->hashContinue.SetNull();
                    }
                }
            }
            else if (inv.type == MSG_TX || inv.type == MSG_WITNESS_TX)
            {
                
                bool push = false;
                auto mi = mapRelay.find(inv.hash);
                if (mi != mapRelay.end()) {
                    pfrom->PushMessageWithFlag(inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0, NetMsgType::TX, *mi->second);
                    push = true;
                } else if (pfrom->timeLastMempoolReq) {
                    auto txinfo = mempool.info(inv.hash);