When running walletpassphrase on a large wallet.dat (ie about 300,000 segwit P2SH addresses) the command sometimes takes a very long time, and if command is run multiple times at once (while running slow) it causes bitcoin core to freeze (stops syncing and requires kill -9 to stop/restart)

During the locked up walletpassphrase commands being run the following messages start to appear in the debug.log:

`018-01-24 01:01:04 socket sending timeout: 1201s`

Note that this problem is intermittent, so sometimes the command runs instantly, other times it takes a few minutes, and other times it completely freezes the node.
{
    assert(!m_storage.IsWalletFlagSet(WALLET_FLAG_DISABLE_PRIVATE_KEYS));
    CKey key;
    key.MakeNewKey(true);
    return DeriveNewSeed(key);
}
CPubKey LegacyScriptPubKeyMan::DeriveNewSeed(const CKey& key)
{
    int64_t nCreationTime = GetTime();
    CKeyMetadata metadata(nCreationTime);
    
    CPubKey seed = key.GetPubKey();
    assert(key.VerifyPubKey(seed));
    
    metadata.hdKeypath     = "s";
    metadata.has_key_origin = false;
    metadata.hd_seed_id = seed.GetID();
    {
        LOCK(cs_KeyStore);
        
        mapKeyMetadata[seed.GetID()] = metadata;
        
        if (!AddKeyPubKey(key, seed))
            throw std::runtime_error(std::string(__func__) + ": AddKeyPubKey failed");
    }
    return seed;
}
void LegacyScriptPubKeyMan::SetHDSeed(const CPubKey& seed)