Mistakes can happen without grift or delusion. A fighter pilot who spends an entire career training against fighter-sized opponents might honestly mistake a small nearby slow-moving drone for a fighter-sized distant fast-moving drone. A radar tech might see returns that fly away at unearthly speeds because that's how jamming works (create fake bait return, fly it away).

But repeated, insistent refusal to engage with obvious dull alternative hypotheses? Yeah, that's delusion / grift.