Does anyone know why an Italian bottle should be a disaster?

OED:

The fig. use of the phrase far fiasco (lit. ‘to make a bottle’) in the sense ‘to break down or fail in a performance’ is of obscure origin; Italian etymologists have proposed various guesses, and alleged incidents in Italian theatrical history are related to account for it.

So, no.

The Maven’s Word of the Day gives some background to the history of Italian and English usage, and details one of the speculative origin theories mentioned by OED above:

But why is “making a bottle” equated with failure? The Barnhart Dictionary of Etymology offers a tantalizing suggestion, “The sense development is unknown, but one of many explanations refers to the alleged practice of Venetian glassmakers setting aside imperfect glass to make a common bottle or flask.” That sounds very plausible to me. In other words, the Venetian glassmakers were probably engaged in something much more difficult than a mere wine bottle, but if they made a mistake, they could always convert the error into a fiasco.

Without evidence, of course, the speculation has no more validity than any other.

Note first that my ignorance of Italian is very advanced, you might say near total.

The Garzanti Italian dictionary says “fare fiasco” is possibly from theater jargon, otherwise not definitely explained.

Note however that “fare fico” means/meant about the same. I find evidence of this equivalence in Italian as early as 1857.

Can one of these be originally a humorous malapropism? Or maybe a euphemism? Or even a dysphemism? Which one? Or maybe both?

Cf. “fica” = “vulva”, and the contemptuous hand-gesture called the “fig” ("fare la fica").

Ah, the fig!

PISTOL: 
Die and be damn’d! and figo for thy friendship!

FLUELLEN: 
It is well.

PISTOL: 
The fig of Spain!
[Exit.]

Hen. V, III, vi

Van Dale says that despite various attempts, no satisfactory etymology has been given yet.
Van Dale does point out that the Italian word is of Germanic origin. With a ‘perhaps’ they suggest that it could be reminiscent of a punishment for quarrelsome women in the Middle Ages, who had to wear a bottle shaped stone around their necks and carry it around the city: this may be reflected in the old sayings Mdu. steen dragen (to carry a stone) and HG eine Schandflasche (a scorn bottle).

And FTR the Dutch word for ‘bottle’ is ‘fles’ (cf. NHG Flasche).