There's no inability to form invisible mental images, Invisible images is when 100% of people don't actually see mental images because they don't see it with their actual eyes. the word ''image'' and ''images'' in the brain means mental representation, but not visual representation in the mind, so therefore, A lot of people form invisible images in their brain.
There's a several papers but not hundreds of them, but there's still no evidence, so therefore the phenomenon is not real and I'm sorry if I'm pounding the table.
I don't have aphantasia, I even If I don't see visible mental images, I don't have it and I don't how forming visible mental images work or look like, The phenomenon is not real. While a lot of people form invisible images when awake and only form mental images in dreams. All people think in representations of things like me and people think in concepts like me and form invisible images without forming visible mental images like me. All brains are different whether they brains form visible mental images or invisible images without visualizing visible mental images, All people think, but all people don't visualize visible mental images. All people don't think in words and sentences, They think in representations of things without forming visible mental images, concepts, but they don't visualize visible mental images, but they form invisible images when they don't see mental images.
Sorry for fallacious reasoning, I'm ending this thread now because the phenomenon is not real and there's no validated diagnosis on it, there is no evidence of it, so it's not real nor recognized phenomenon. There will be no further replies on this.