I think everybody sees this with Biden. Senility is indeed overtaking him.
He may be in the early stages of dementia. My mother suffered from this near the end of her life. You could have a perfectly normal conversation with her, then suddenly, she would start talking in great detail about things that never happened. To someone who did not know her well, the story would sound plausible, but those close to her knew it never happened. I thought about that when Biden told his fabricated story about pinning a medal on a soldier in Afghanistan. Maybe Biden was just lying, or maybe he really believed what he was saying.