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);
    WalletBatch batch(m_storage.GetDatabase());
    
    int64_t oldestKey = GetOldestKeyTimeInPool(setExternalKeyPool, batch);
    if (IsHDEnabled() && m_storage.CanSupportFeature(FEATURE_HD_SPLIT)) {
        oldestKey = std::max(GetOldestKeyTimeInPool(setInternalKeyPool, batch), oldestKey);
        if (!set_pre_split_keypool.empty()) {
            oldestKey = std::max(GetOldestKeyTimeInPool(set_pre_split_keypool, batch), oldestKey);
        }
    }
    return oldestKey;
}
size_t LegacyScriptPubKeyMan::KeypoolCountExternalKeys() const
{
    LOCK(cs_KeyStore);
    return setExternalKeyPool.size() + set_pre_split_keypool.size();
}
unsigned int LegacyScriptPubKeyMan::GetKeyPoolSize() const
{
    LOCK(cs_KeyStore);
    return setInternalKeyPool.size() + setExternalKeyPool.size() + set_pre_split_keypool.size();
}
int64_t LegacyScriptPubKeyMan::GetTimeFirstKey() const
{
    LOCK(cs_KeyStore);
    return nTimeFirstKey;
}
std::unique_ptr<SigningProvider> LegacyScriptPubKeyMan::GetSolvingProvider(const CScript& script) const