Revealing mistake: When Han shoots at Bruce Willis and the others with the Gatling gun, we see cartridges on the ground. You can tell that they are all blanks. The tip is jagged and has been closed - live ammo just has an open hole where the bullet was.
Revealing mistake: Near the end it cuts to a scene where there is a small group of musicians playing classical music. In the centre is a male violinist playing but his bow is about 3 inches away from the violin.
Revealing mistake: When Han is firing the Gatling gun at Frank and Marvin, he is on one side of the street, firing across the street and through the parked cars. Frank and Marvin are lying on the ground on the sidewalk, but some of the bullets' exit holes (after shooting through the vehicles) fold inwards, when they should have bent the metal outwards. (00:49:30)
Revealing mistake: After Bailey stabs multiple people, there's no blood on the knife used at any point. (01:50:00)
Revealing mistake: When Han is firing the chain gun at Frank and Marvin in Paris, the shell casings and links are shown. The shell casings have crimped ends which are used in blanks. (00:48:15)
Chosen answer: Insane in the sense that he wasn't completely mentally capable? Yes. Insane in that he wanted to blow them up? No. He was heavily medicated while in care and so his ramblings and confusion are supposed to be perceived as genuine. Once he starts commenting that he is beginning to remember his past, we then assume that he realizes what his original intentions were and somehow manages to contact the other agency.
But Bailey states before he kills Katja that he was responsible for leaking the post online that Marvin saw which started the whole thing. He said he took a guard's phone to do it. I believe he was very aware and was just "playing" everyone.