Thug, to comment on your comment: if you remember correctly, Sandy did not like the wine and did not want to drink it. So if she passed it back to Jan she would not have wanted it back, so I think this is probably a slip-up.
No, Jan was trying to shove it into Sandy's hand. So it only looks like Sandy has it, then Jan, then Sandy. Jan put it into Sandy's hand, Sandy handed it back. Then Rizzo started teasing her about not drinking, so Sandy took it back from Jan.
What about the fan on the wall, it disappears and then reappears again but only when it reappears it is on the headboard and not on the wall. Also in the same scene if you look at the headboard it is messy and clean several times while Rizzo is singing.
I've noticed the bottle swap too. If everyone was paying attention to the movie they would know that they bottle was passed back and forth after sandy took a drink of wine. So whoever said that sandy and jan kept passing it back and forth because she was to scared to take a drink was wrong. It was just an editing mistake. No big deal.
I saw this slip-up! It is very noticeable when you know what you are looking for. Sandy has the bottle and then the girl with the pigtails has it and then Sandy again and the girl with the pigtails is eating a twinkie. This all happens when they are talking about peircing Sandy's ears!