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 (!CanGetAddresses(internal)) {
        return false;
    }
    if (!ReserveKeyFromKeyPool(index, keypool, internal)) {
        return false;
    }
    address = GetDestinationForKey(keypool.vchPubKey, type);
    return true;
}
void LegacyScriptPubKeyMan::MarkUnusedAddresses(const CScript& script)