Continuity mistake: After Dory reads the wall map while she's in the glass carafe, when Hank hides behind the rolling cabinet there's a long shot of the corridor with him at the far wall, then in the next shot from behind Hank a drinking fountain has suddenly appeared on the wall to the left, between two pictures.
Continuity mistake: When Dory reads the word "Destiny" on the white bucket, its handle is attached over the letter "t", but when Dory forces the glass carafe to tip over, now the handle is attached over the letter "e."
Continuity mistake: When Carol, the MLI employee, is first seen carrying the white bucket in the corridor and also when Carol thinks she located Hank, the bucket has absolutely no writing on it where the handle's attached on both sides, but when Dory looks down at the bucket suddenly "Destiny" is written on it.
Continuity mistake: When Dory and Hank are in the stroller trying to get to the Open Ocean exhibit, Hank steers the stroller right into a girl wearing a striped top and holding a cup of popcorn, but a few shots later that same girl is now wearing a light pink top when she's on her knees with the spilled popcorn.
Chosen answer: In the absence of a neuropsychological work-up, we have only Dory's word for it: "I have short term memory loss...It runs in my family...at least, I think it does." So, Dory believes it to be genetic. At least, I think she does.
Michael Albert