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.
bool CanGenerateKeys() const;
    
    CPubKey GenerateNewSeed();
    
    CPubKey DeriveNewSeed(const CKey& key);
    /* Set the current HD seed (will reset the chain child index counters)
       Sets the seed's version based on the current wallet version (so the
       caller must ensure the current wallet version is correct before calling
       this function). */
    void SetHDSeed(const CPubKey& key);
    /**
     * Explicitly make the wallet learn the related scripts for outputs to the
     * given key. This is purely to make the wallet file compatible with older
     * software, as FillableSigningProvider automatically does this implicitly for all
     * keys now.
     */
    void LearnRelatedScripts(const CPubKey& key, OutputType);
    /**
     * Same as LearnRelatedScripts, but when the OutputType is not known (and could
     * be anything).
     */
    void LearnAllRelatedScripts(const CPubKey& key);
    /**
     * Marks all keys in the keypool up to and including reserve_key as used.
     */
    void MarkReserveKeysAsUsed(int64_t keypool_id) EXCLUSIVE_LOCKS_REQUIRED(cs_KeyStore);
    const std::map<CKeyID, int64_t>& GetAllReserveKeys() const { return m_pool_key_to_index; }
    std::set<CKeyID> GetKeys() const override;
};
class LegacySigningProvider : public SigningProvider