Other mistake: When Clarice goes to Crawford's office, she sees on the board a newspaper article titled "Bill skins fifth", but the article is not about Buffalo Bill. It's about Hannibal Lecter (his capture, the charges against him and so on). Nowhere is Bill mentioned. (00:05:50)
Other mistake: Clarice on the plane with Crawford is flipping through the report about the first victim (third found). Despite being a report on a victim of a case already thoroughly analyzed, it is lacking pretty much every detail about the victim other than the name and an incomplete address, and the data about the coroner in its second page point at Cleveland but with a California 408 area code (this page is realistically visible in detail only through slow motion, even if the relevant aspects - zip code and town name - can be spotted at normal speed). Finally, when Clarice turns page in the next shot to get to the photo part, the page is different. (00:36:15)
Other mistake: Exterior views of Buffalo Bill's house showed the house was not very big and his yard space was limited. The amount of rooms, their sizes, and hall space purportedly in the basement were too excessive to believably be under that house. (00:49:20)
Other mistake: In Memphis, the vain Dr. Chilton is giving an interview in front of the courthouse. So the captions say, because the building he is talking in front of (in actuality the Soldiers and Sailors Memorial Hall and Museum in Pittsburg) has just a dimly lit "Shelby County War Museum" sign. From the look of the hall, the latter seems to be correct. (01:05:10)
Other mistake: After Clarice is finished interviewing Frederica Bimmel's friend, they cut to the abandoned house in Calumet City IL. The front yard is full of leaves, but yet there is only 1 lone (pine) tree in the yard, and the homes on either side do not have visible trees either.
Answer: The body in the bathtub is Mrs. Lippman, the previous owner of Jame Gumb's home. Notice the long grey hair coming from the scalp. He would have wanted someone young, large, and whole.