My understanding is that George Lucas maintains he intended for the Jabba scene to be in the movie, but they lacked the money to create the alien Jabba he wanted using stop motion or something.
It’s exceedingly likely that Jabba was originally intended to be a human; it’s been covered thoroughly here-
https://web.archive.org/web/20140928112036/http://secrethistoryofstarwars.com/jabba.htmlAccording to Paul Hirsh (one of the editors) in his biography, Lucas came up with the alien Jabba idea in post-production, but it had to be dropped due to being impossible to achieve with contemporary special effects technology.
My phone’s protection software through a fit when I tried to follow that link. But it makes sense that Jabba was intended to be human during production. That still leaves us with two scenes that just don’t work together. Oh well! Filmmaking is not always a linear process, and in reality the details of the complications of a movie made half a century ago may remain unknowable.