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.
{
    switch (IsMineInner(*this, script, IsMineSigVersion::TOP)) {
    case IsMineResult::INVALID:
    case IsMineResult::NO:
        return ISMINE_NO;
    case IsMineResult::WATCH_ONLY:
        return ISMINE_WATCH_ONLY;
    case IsMineResult::SPENDABLE:
        return ISMINE_SPENDABLE;
    }
    assert(false);
}
bool LegacyScriptPubKeyMan::CheckDecryptionKey(const CKeyingMaterial& master_key, bool accept_no_keys)
{
    {
        LOCK(cs_KeyStore);