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);
    if (!memonly && !WalletBatch(m_storage.GetDatabase()).WriteHDChain(chain))
        throw std::runtime_error(std::string(__func__) + ": writing chain failed");
    hdChain = chain;
}
bool LegacyScriptPubKeyMan::HaveKey(const CKeyID &address) const
{
    LOCK(cs_KeyStore);
    if (!m_storage.HasEncryptionKeys()) {
        return FillableSigningProvider::HaveKey(address);
    }
    return mapCryptedKeys.count(address) > 0;
}
bool LegacyScriptPubKeyMan::GetKey(const CKeyID &address, CKey& keyOut) const
{
    LOCK(cs_KeyStore);
    if (!m_storage.HasEncryptionKeys()) {
        return FillableSigningProvider::GetKey(address, keyOut);
    }
    CryptedKeyMap::const_iterator mi = mapCryptedKeys.find(address);
    if (mi != mapCryptedKeys.end())
    {
        const CPubKey &vchPubKey = (*mi).second.first;
        const std::vector<unsigned char> &vchCryptedSecret = (*mi).second.second;
        return DecryptKey(m_storage.GetEncryptionKey(), vchCryptedSecret, vchPubKey, keyOut);
    }
    return false;
}
bool LegacyScriptPubKeyMan::GetKeyOrigin(const CKeyID& keyID, KeyOriginInfo& info) const