I will add that I am also experiencing this error.
A "Veteran" user from the Discord server advised that I fix the issue "by removing one of the files that tracks subscribed compositions". The only file that I could find that displayed subscribed items, including compositions, was a file called " subscribedcontent.list " located in "...\Documents\Arma 3\Saved\steam\meta". It's true that compositions with the ID can be found there, when it is unbinarised. And it's true that the offending (in my case 2) compositions could not be found anymore on the workshop. However, neither removing the specific entries in the file, nor deleting the entire file, fixed the issue.

Thank you for the Christmas present! Good tidings to you, and your kin.
__________(█)
_______██████
_____ ████████
___███████████
___ (░░░░░░░)░░░)
___(░(░█░░█░)░░░)
__ (░░(░░●░░░)░░░)
__ (░░░░◡░░)░░░░)
_██(░░░░░░░░░░)██
_███(░░░░░░░░░)███
████ ██(░░░)██ ████
████ █████████ ███
████ ████░████ ███
(░░)_ ▓▓▓▓▌▓▐▓▓▓_(░░)
(██) ███████████ (██)
_____█████░█████_▓▓▓\
_____█████-,█████▓▓▓▓▓)
_____█████-,█████▓▓▓▓▓)
___(░░░░░░)(░░░░░) ▓▓▓▓)
______(███)_(███)▓▓▓▓▓▓)
____ (████)_(████)▓▓▓▓▓)

Note: although I have received help from the Discord on uploading images and files (it's drag and drop; no buttons... wish I could create a feedback ticket on feedback tickets..), I unfortunately still can't play this mission.

PS I have a screenshot and an error report. How do I attach these to this bug report?