Robert Rubin, Going to Hell in a Hen Basket: An Illustrated Dictionary of Modern Malapropisms (2015) has this discussion of "chalk-full" and "chock it up to":
chalk-full V: chock it up to. Confuses chockfull with chalk it up to. Chock-full is an old phrase, perhaps coming from choke-full or full to choking. Chalk it up to comes from chalk tally marks on a slate. Chock marks indicate where to put wooden chocks (or wedges) and may be confused with chalk marks.
A Google Books search finds more than 40 unique matches for "chock it up to" in which the author presumably meant to say "chalk it up to" but either spelled chalk wrong or didn't know the correct traditional spelling of the idiom. Tellingly, the vast majority of these 40+ instances come from the past ten years, suggesting either that chock is emerging as a legitimate variant spelling of chalk in this situation or that many publishers no longer employ copy editors to find and correct mistakes of this type.
To complicate matters, a Google Books search finds a number of instances of "chock it up" in which chock means "to stabilize with another object in order to prevent [a thing] from moving. Thus, for example, from John Weiss, Life and Correspondence of Theod. Parker, Minister of the 28th Congregational Society, Boston (1863):
This writing-desk I sit at {at Montreux} is so made that a book will slide down the leaf, and I must chock it up.
From "Mending the Road From Rich Mountain," in The Breeder's Gazette (March 26, 1913):
"Well, wait, I'll call my man out of the field," said King Wheeler.
"No do not do that; you and I can manage it [removing an obstructing stone from the roadway] very nicely. Please get down and chock it up with this small stone as I pry it up and presently we will be able to manage it."
From "Flight Quarters": The War Story of the U.S.S. Belleau Wood (1946) [combined snippets]:
At the foot of the elevator a dollyman waits. To the commands of: "To the starboard", "To the port", and "Hold that, you wanna break a wing?" the hangar dock crew pushes the dud in spot. "Chock it up", the coxswain orders, and while the two mechanics roll up a stand underneath the engine a trouble shooter jumps into the cockpit.
And from Industrial Supervisor, volumes 22–24 (1954[?]) [combined snippets]:
Secondly, when you pick up small heavy boxes, like small crates of machine parts, you run a chance of getting your fingers smashed. So before you pick up such an object, chock it up. Stick a chip or a piece of wood under it to raise it from the floor a little bit so you can get your hands under it for a good grip.
Conclusion
The idiom "chock it up" can be correct in instances where it means to insert wedge-shaped blocks or other objects next to something to prevent it from rolling, dropping, or coming loose; but it is not correct—at least not yet—in place of chalk it up in the idiomatic expression "chalk it up to X."