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.
{
    for (const valtype& pubkey : pubkeys) {
        CKeyID keyID = CPubKey(pubkey).GetID();
        if (!keystore.HaveKey(keyID)) return false;
    }
    return true;
}
IsMineResult IsMineInner(const LegacyScriptPubKeyMan& keystore, const CScript& scriptPubKey, IsMineSigVersion sigversion, bool recurse_scripthash=true)
{
    IsMineResult ret = IsMineResult::NO;
    std::vector<valtype> vSolutions;
    txnouttype whichType = Solver(scriptPubKey, vSolutions);
    CKeyID keyID;
    switch (whichType)
    {
    case TX_NONSTANDARD:
    case TX_NULL_DATA:
    case TX_WITNESS_UNKNOWN:
        break;
    case TX_PUBKEY:
        keyID = CPubKey(vSolutions[0]).GetID();
        if (!PermitsUncompressed(sigversion) && vSolutions[0].size() != 33) {
            return IsMineResult::INVALID;
        }
        if (keystore.HaveKey(keyID)) {
            ret = std::max(ret, IsMineResult::SPENDABLE);
        }
        break;