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.
{
    LOCK(cs_KeyStore);
    assert(m_max_keypool_index < std::numeric_limits<int64_t>::max()); 
    int64_t index = ++m_max_keypool_index;
    if (!batch.WritePool(index, CKeyPool(pubkey, internal))) {
        throw std::runtime_error(std::string(__func__) + ": writing imported pubkey failed");
    }
    if (internal) {
        setInternalKeyPool.insert(index);
    } else {
        setExternalKeyPool.insert(index);
    }
    m_pool_key_to_index[pubkey.GetID()] = index;
}
void LegacyScriptPubKeyMan::KeepDestination(int64_t nIndex, const OutputType& type)
{
    
    WalletBatch batch(m_storage.GetDatabase());
    batch.ErasePool(nIndex);
    CPubKey pubkey;
    bool have_pk = GetPubKey(m_index_to_reserved_key.at(nIndex), pubkey);
    assert(have_pk);
    LearnRelatedScripts(pubkey, type);
    m_index_to_reserved_key.erase(nIndex);
    WalletLogPrintf("keypool keep %d\n", nIndex);
}
void LegacyScriptPubKeyMan::ReturnDestination(int64_t nIndex, bool fInternal, const CTxDestination&)