I was waiting for those scenes to be referrenced but didnt want to bloat my initial response with pre-emptive explanations to replies that may not be made.
Firstly, there is nothing showing that the Tie Bombers arent actually launching those bombs, especially since yes, the massive asteroid would have it’s own gravity but not anywhere near enough to make the bombs fall as fast as they do, so therefore one can assume they are propelled by some off-camera force. Whereas we are specifically shown the bombs “dropping” in TLJ with no indication of a self propulsion or launch system.
Secondly, yes once I was old enough to understand and actually thought about it one day, the cave scene certainly doesn’t stack up so well with their casual walk about and use of flimsy little plastic hospital oxygen masks. I think the fact that the space slug itself lives in the vacuum of space and there are “Mynocks” flying about inside speaks to some internal atmosphere the slug creates somehow which more or less accounts for the makeshift masks (this draws on what I said before about sci-fi loosely grounded in reality) but not for the gravity which is an oversight and inconsistent with the general depiction of space within Star Wars. I don’t think anyone claims the originals to be perfect and this is a minor slight at this stage where on first viewing, you’re more concerned with what the characters are concerned about after C3PO and Leia spot some unknown alien creatures through the windows.
In comparison (and I think the difference at least for me) my suspension of disbelief is already broken and trampled upon by the time the bombs drop in TLJ from the Hux prank call, his de-toothing by Snoke, the general and almost comical (if it wasn’t detracting from the story) incompetence of the First Order and BB8 plugging electrical shorts as if they were water leaks?
The thing about both of the above ESB scenes as well, is that despite their interpretations and any inherent inaccuracies, both are localised to the massive asteroid and so there is still a loose link of the gravity being generated by it that you can attribute it’s source to if you don’t over analyse it. Whereas the TLJ scene is literally in the middle of space away from the planet, so where is this origin of gravity and what determines it’s direction at any given time? These questions are readily apparent on first viewing without having to specifically think about the scenario.
Anyway, my main point I was initially making before we started comparing depictions of gravity in Star Wars is that I dont see how in anyway Luke falling into the garbage disposal tubes on Cloud City constitutes a plot hole, especially in comparison to the TLJ bomb drop which is such a plain and obvious issue to most people when the scene is set in space, no matter how loosely you want to link your own understanding of Star Wars physics to real life.