Charles Dickens' Unsolved Texts in Shorthand

In February 2022, Charles Dickens' letter in shorthand was cracked (for about 60%) (The Dickens Code, Open Culture, The Dickens Project). It remained unsolved for over 150 years (called the Tavistock letter from the letterhead).
I thank D.P.J.A. Scheers, who authored "The Shorthand of Charles Dickens" (Academia.edu) last year, for attracting my attention to this. (He is credited as one of the contributors to the solution (Roll of Honour).) Although shorthand is different from a code/cipher, it is sometimes called as such (a famous example is Samuel Pepys' diary, mentioned in a previous post).

Dickens taught himself shorthand as a teenager. There were many shorthand systems, but what he picked was Gurney's Brachygraphy, one notoriously difficult to master. Struggles with shorthand are mentioned in the semi-autobiographical novel, David Copperfield (Ch. 38) (The Dickens Code). Moreover, Dickens adapted the system as he used it, which added difficulty in reading surviving texts in shorthand left by him.
The 60% solution (pdf) of the Tavistock letter was achieved by contributors around the world in response to a call by the Dickens code project. (Since 40% is still unread, there is still room to make contributions, though the contest is closed.)
There are eleven shorthand texts left by Dickens (Hugo Bowles, "Dickens's Shorthand Manuscripts", Dickens Quarterly, Johns Hopkins University Press, Volume 35, Number 1, March 2018 (Project MUSE). Bowles is a pioneer in this field and authored "Dickens's Shorthand Deciphered by Identifying 'Sydney Smith' Source Text", Notes and Queries 64.4 (2017): 614-17 (which I have not seen). Some unsolved shorthand texts are presented as challenges at The Dickens Code website. One is still open for a few more days!