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.

CleanupBlockRevFiles();
                }
                if (!LoadBlockIndex()) {
                    strLoadError = _("Error loading block database");
                    break;
                }
                
                
                if (!mapBlockIndex.empty() && mapBlockIndex.count(chainparams.GetConsensus().hashGenesisBlock) == 0)
                    return InitError(_("Incorrect or no genesis block found. Wrong datadir for network?"));
                
                if (!InitBlockIndex(chainparams)) {
                    strLoadError = _("Error initializing block database");
                    break;
                }
                
                if (fTxIndex != GetBoolArg("-txindex", DEFAULT_TXINDEX)) {
                    strLoadError = _("You need to rebuild the database using -reindex-chainstate to change -txindex");
                    break;
                }
                
                
                if (fHavePruned && !fPruneMode) {
                    strLoadError = _("You need to rebuild the database using -reindex to go back to unpruned mode.  This will redownload the entire blockchain");
                    break;
                }
                if (!fReindex) {
                    uiInterface.InitMessage(_("Rewinding blocks..."));
                    if (!RewindBlockIndex(chainparams)) {
                        strLoadError = _("Unable to rewind the database to a pre-fork state. You will need to redownload the blockchain");