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.
{
    return !hdChain.seed_id.IsNull();
}
bool LegacyScriptPubKeyMan::CanGetAddresses(bool internal) const
{
    LOCK(cs_KeyStore);
    
    bool keypool_has_keys;
    if (internal && m_storage.CanSupportFeature(FEATURE_HD_SPLIT)) {
        keypool_has_keys = setInternalKeyPool.size() > 0;
    } else {
        keypool_has_keys = KeypoolCountExternalKeys() > 0;
    }
    
    if (!keypool_has_keys) {
        return CanGenerateKeys();
    }
    return keypool_has_keys;
}
bool LegacyScriptPubKeyMan::Upgrade(int prev_version, bilingual_str& error)