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.
{
    CKeyMetadata meta;
    {
        LOCK(cs_KeyStore);
        auto it = mapKeyMetadata.find(keyID);
        if (it != mapKeyMetadata.end()) {
            meta = it->second;
        }
    }
    if (meta.has_key_origin) {
        std::copy(meta.key_origin.fingerprint, meta.key_origin.fingerprint + 4, info.fingerprint);
        info.path = meta.key_origin.path;
    } else { 
        std::copy(keyID.begin(), keyID.begin() + 4, info.fingerprint);
    }
    return true;
}
bool LegacyScriptPubKeyMan::GetWatchPubKey(const CKeyID &address, CPubKey &pubkey_out) const