Phrase for the opposite of "foolproof"

Solution 1:

This UI is:
- Nonobvious = Not easily discovered, seen, or understood
- Unclear = not clear
- Counterintuitive = contrary to what one would intuitively expect
- Illogical = not observing the principles of logic

It is difficult to correct someone without risking direct or implicit criticism.

Solution 2:

Misleading

Giving the wrong idea or impression - OOD

A confirmation pop-up is expected to ask if the user wants to continue. When it asks the negation of what is expected many people can be expected to answer incorrectly.

Solution 3:

foolprone

something or someone that is at high risk of foolish actions or ideas being brought upon them and cannot become rid of such actions or ideas, no matter the nature of foolishness; antonym of foolproof.

(courtesy of https://definithing.com/foolprone/ & https://www.urbandictionary.com/define.php?term=foolprone)

Arguably, it's a made-up word, but it does exist in the wild, and it nice enough as far as neologisms go IMVHO.

Solution 4:

Probably not very common outside of programming circles, but a "footgun" is something which makes it very easy for the user to shoot themselves in the foot. It is fairly negative towards the feature, but other than that it doesn't criticize the creator (as far as I'm aware).

From https://en.wiktionary.org/wiki/footgun :

(programming slang, humorous, derogatory) Any feature whose addition to a product results in the user shooting themselves in the foot.

Solution 5:

I read the title of the question and immediately thought of error prone—before reading the rest of the question. I personally don't think there is a better phrase than that. It's open to interpretation and context what the reason is behind the possible errors.

Having said that, another possible word is fallible: