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.

return InitError(strprintf(_("Cannot obtain a lock on data directory %s. %s is probably already running.") + " %s.", strDataDir, _(PACKAGE_NAME), e.what()));
    }
#ifndef WIN32
    CreatePidFile(GetPidFile(), getpid());
#endif
    if (GetBoolArg("-shrinkdebugfile", !fDebug))
        ShrinkDebugFile();
    if (fPrintToDebugLog)
        OpenDebugLog();
    if (!fLogTimestamps)
        LogPrintf("Startup time: %s\n", DateTimeStrFormat("%Y-%m-%d %H:%M:%S", GetTime()));
    LogPrintf("Default data directory %s\n", GetDefaultDataDir().string());
    LogPrintf("Using data directory %s\n", strDataDir);
    LogPrintf("Using config file %s\n", GetConfigFile().string());
    LogPrintf("Using at most %i connections (%i file descriptors available)\n", nMaxConnections, nFD);
    std::ostringstream strErrors;
    LogPrintf("Using %u threads for script verification\n", nScriptCheckThreads);
    if (nScriptCheckThreads) {
        for (int i=0; i<nScriptCheckThreads-1; i++)
            threadGroup.create_thread(&ThreadScriptCheck);
    }
    
    CScheduler::Function serviceLoop = boost::bind(&CScheduler::serviceQueue, &scheduler);
    threadGroup.create_thread(boost::bind(&TraceThread<CScheduler::Function>, "scheduler", serviceLoop));
    /* Start the RPC server already.  It will be started in "warmup" mode
     * and not really process calls already (but it will signify connections
     * that the server is there and will be ready later).  Warmup mode will
     * be disabled when initialisation is finished.
     */
    if (fServer)