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.

#include "util.h"
#include "utilmoneystr.h"
#include "validationinterface.h"
#ifdef ENABLE_WALLET
#include "wallet/wallet.h"
#endif
#include <stdint.h>
#include <stdio.h>
#ifndef WIN32
#include <signal.h>
#endif
#include <boost/algorithm/string/classification.hpp>
#include <boost/algorithm/string/predicate.hpp>
#include <boost/algorithm/string/replace.hpp>
#include <boost/algorithm/string/split.hpp>
#include <boost/bind.hpp>
#include <boost/filesystem.hpp>
#include <boost/function.hpp>
#include <boost/interprocess/sync/file_lock.hpp>
#include <boost/thread.hpp>
#include <openssl/crypto.h>
#if ENABLE_ZMQ
#include "zmq/zmqnotificationinterface.h"
#endif
using namespace std;
bool fFeeEstimatesInitialized = false;
static const bool DEFAULT_PROXYRANDOMIZE = true;
static const bool DEFAULT_REST_ENABLE = false;
static const bool DEFAULT_DISABLE_SAFEMODE = false;
static const bool DEFAULT_STOPAFTERBLOCKIMPORT = false;