Time travel in Doraemon - was the Stable Timeloop effect ever really adverted?

Question

The basic premise in the Japanese manga/anime Doraemon is that the titular character - a robot cat from the 22 century - was sent to the past to help Nobita Nobi to improve his future. In the first episode of the show, Nobita grandson Sewashi Nobi specifies that due to Nobita poor grades in school he meet many failures in his life, causing his descendants a lot of problem.

Doraemon was sent to the past so that Nobita could improve and become a better person. Based on many references in the show, apparently the future did indeed change - Sewashi states that Nobita was originally going to get married to "Gian" sister Jaiko but now the future shows him married to Shizuka instead.

Given these premises, it seems that time travel can change the present/future if the past is changed.

Yet every single other instance of time travel in the show seem to end up in a stable time loop... Here are just some example that come to mind:

• a coin is stolen from an house, no sign of infraction. Suneo points out that the only one able to perform such feat would be Doraemon using his Anywhere Door. Doreamon proceedes to go to the past to see what really happened, but when he find nothing he decides to take the coin to avoid it being stolen. He quickly realizes he just caused the coin disappearance.
• Nobita's parents have a argument on who of them proposed to the other, each one claiming it was the other. Nobita and Doraemon go to the past to check, they end up causing the issue (afraid that Nobita parents would never get together, Doraemon uses a trick that end up making each of them think it was the other who first proposed)
• Nobita hears a tale from his dad - when he was young he meet a weird girl that gave him some chocolate. Wondering on the identity of the girl, Nobita and Doraemon use the time machine again. Due to some weird series of events, Nobita ends up to be the one his young dad saw in the first place
• In another episode Nobita causes a problem by sending to future Doraemon a picture of them together - this makes Doraemon worry since he was originally yellow and seeing the photo (he is currently blue) could cause his future self a trauma and change history. At the same time he also states to remember something that "made him happy" the day he was born. Nobita and Doraemon manage to recover the photo, but the attached letter that Nobita sent with it ends up being the something that made future Doraemon happy and he remembered all along.
• Even what seems to be the only episode where story risk to be changed actually becomes a sort of loop. In "Nobita disappeared?" Nobita travels to the past to help his future father to pursue his dream as an artist. In doing so, he seems to change history so that his father would never marry his mother, and Doraemon fears that when the "ripple effect" in time flow would catch up, Nobita would disappear from existence. Yet, the problem basically solves itself and his father end up meeting his mother anyway (to the point it almost seems they actually caused it in the first place - Nobisuke meets Tamako while leaving Kaneko house and probably would never have been there if it was not for Nobita interference)
• the plot of the movie "Doraemon: New Nobita's Great Demon—Peko and the Exploration Party of Five" basically hinges around a loop. During the last "battle" in the movie, Shizuka uses one of Doraemon gadget to force a loop, making their future versions from the next day come back with the time machine to help them. This end up in two Gian, Suneo, Shizuka and Nobita. In doing so, Shizuka fulfills a prophecy about the number of heroes that would "save the day"

I could make some more examples but it should be clear by now. Every time Doraemon and Nobita use the time-travel machine apparently they end up in a stable time loop where all the consequences of their action where already in place from the start. All seems to point to a "Destiny is already written" trope, and yet the show premise is that Nobita managed to change his future.

I am therefore asking - outside of the obvious case of Nobita future, are there any actual example of future/past event being changed because of time travel in the show? I am aware that multiple episodes mention a "Time Police" which duty apparently is to prevent people from messing with history, but every instance I could think of has just the police preventing people from abusing time travel (for example poachers hunting dinosaurs) than actually preventing time changes.

Answer 1

One notable example is in the Nobita and the Steel Corps manga and movie (particularly the subsequent New Steel Corps remake), towards the end of the movie

Shizuka goes back in time with Lilulu 30k years into the past of Megatopia, who (after the Professor collapses while removing their competitive directives) uses her feelings for Nobita and friends along with Pippo to reprogram robot army's ancestors, effectively wiping the Army (via a butterfly effect) from the current timeline (as a result of Lilulu's actions, causing a grandfather paradox of sorts) along with Lilulu and Pippo, just as Nobita and co. are finally overpowered the force of the Robot Army.
(Wikipedia link to the full plot available here)

Albeit technically a closed loop, IMO an interesting time travel story to consider involves the last Doraemon published chapter of the original manga "The Man from Planet Garapa" (previously released as vol. 44.5, now collected as the last chapter in vol. 45). A plot involving Nobita going into the future to get his allowance early results into him discovering that humanoid ants seemingly have taken over the local neighborhood, he goes back to warn Doraemon, but in turn sets off in creating a series of loops (involving another future version of himself in his current timeline) that lead up to the creation of such a future that, ironically, thanks to these subsequent acts, resolves itself, with a bit of effort and coincidental timing from them. No other time traveling plot devices except for the time machine are involved (even then it doesn't really play a major role in the end).

Answer 2

Another possible example I recently discovered is found in the episode "Shizuka-chan's Worst Birthday Ever" (Original Title: しずかちゃんの最悪な誕生日 - shizukachan no saiakuna tanjōbi).

The entire plot of the episode revolves around Doraemon and Nobita using the time machine to purposely change the past in order to prevent a series of unfortunate events that struck Shizuka on the day of her birthday. Originally, Shizuka arrived late at her birthday party, almost crying for the bad day she had (lost her wallet, had a bucket of green paint fall on her and so on) but by the end of the episode the duo was able to correct the past so that she wouldn't have any problem - meaning that they did indeed alter the original timeline.