Unreliable narrators need to add something to the story. They aren’t an excuse for poor storytelling and inconsistencies.
If you have an unreliable narrator, you should be doing twice as much work in your plotting! At every turn of the story, you need to know both what’s actually happening AND what your narrator thinks is happening.
When you’re right, you’re right. And you’re right.
Not only does the author need to know what’s happening on both layers of story, they need to actually write in clues for the reader to telegraph the lower, “true,” layer of the story so the reader is capable of figuring it out if they choose to read closely. Without that double work, an unreliable narrator cannot perform its literary function.
It is the evidence of the truth, not the lie the narrator tells, that makes a narrator unreliable. Otherwise they are just a liar which the audience is incapable of catching due to the hobbling imposed by the medium. Which means the lie may as well be the truth, making it serve no function as a lie.