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 UINT256_ONE();
}
/**
 * Update wallet first key creation time. This should be called whenever keys
 * are added to the wallet, with the oldest key creation time.
 */
void LegacyScriptPubKeyMan::UpdateTimeFirstKey(int64_t nCreateTime)
{
    AssertLockHeld(cs_KeyStore);
    if (nCreateTime <= 1) {
        
        
        nTimeFirstKey = 1;
    } else if (!nTimeFirstKey || nCreateTime < nTimeFirstKey) {
        nTimeFirstKey = nCreateTime;
    }
}
bool LegacyScriptPubKeyMan::LoadKey(const CKey& key, const CPubKey &pubkey)
{
    return AddKeyPubKeyInner(key, pubkey);
}
bool LegacyScriptPubKeyMan::AddKeyPubKey(const CKey& secret, const CPubKey &pubkey)