When Astrid brings her husband dinner and then checks his phone, her wedding ring jumps from her middle finger during the interaction with her husband, to her ring finger while working with the phone.
When Rachel and Peik Lin are first going to Nick's family's home and can't seem to find it, Peik remarks it's like they are in a jungle. She says they are in the middle of nowhere. Security shows up and checks them out. When Peik asks them if they know where the Young house is, the shot changes from the car interior to immediately in front of it. They are literally feet from the gate--hardly in the middle of nowhere.
In the very last last scene where Rachel and Nick are celebrating their engagement with friends and family at the top of the Sands hotel, TA Curtis is briefly seen in the crowd as one of the party attendees. Given that he is supposed to be Rachel's colleague at NYU and the party occurred with little notice, his appearance is odd.
When Nick and Rachel are talking on the hotel couch after the bachelor/bachelorette parties, Rachel's arms jump from crossed, to uncrossed, to crossed between scenes.
When Nick invites Rachel to Singapore, he says "Singapore for Spring Break". This would place the timing of the film between March and April of the calendar year. However, the Tan Hua (Queen of the Night Flower), which blooms on the second night after they arrive, only blooms between July and October.
During her massage, Rachel jokingly remarks that she thinks her masseuse got her pregnant. Since a masseuse is a woman, one woman can't get another pregnant. The male equivalent of a masseuse is a masseur (from the French).
Napoléon Bonaparte did not actually say "Let China sleep, for when she wakes, she will wake the world." The misquote is a tribute to 55 Days at Peking (1963).
When Nick (Henry Golding) and Rachel (Constance Wu) arrive from New York at Terminal 3 at Singapore's Changi Airport, the "Departure" sign can be seen at the far left. The actual Arrivals is on a different floor. The Arrivals hall has lower ceilings and it is harder to film as most of it is secured with arriving passengers. The Departure level is more visually impressive and easier to film.
The only airline to offer a non-stop flight from New York to Singapore is Singapore Airlines (who declined to appear in the movie) and flies from EWR to SIN using the Airbus A850-900 ULR as it is the only plane capable of doing the 15340 kilometer route.
That plane configuration only features a business and premium economy cabin, so Nick and Rachel wouldn't have been able to fly in first, nor would there have been a bar on board.
Further, Emirates is the only airline to fly the A380 on a JFK to SIN route and that would require a stop in Dubai, which the flight map doesn't allow for, nor does it match the substitute airline Asean Oceanic Airways which would likely be based in Asia and therefore use a country in that realm as their hub.
That plane configuration only features a business and premium economy cabin, so Nick and Rachel wouldn't have been able to fly in first, nor would there have been a bar on board.
Further, Emirates is the only airline to fly the A380 on a JFK to SIN route and that would require a stop in Dubai, which the flight map doesn't allow for, nor does it match the substitute airline Asean Oceanic Airways which would likely be based in Asia and therefore use a country in that realm as their hub.
When the plane flight graphic displays the flight from New York to Singapore á la Indiana Jones, the line drawn goes over Europe. Planes would fly almost due north (358 degrees) to take the shortest route for this long (nearly 10,000 km) flight, i.e., over the North Pole and Russia.
When the map of Singapore is shown and the indicator showing that Nick and Rachel's flight has arrived into Singapore, it stops at an area close to the nation's harbour in south Singapore rather than Changi Airport, which is on the extreme east of the island.
When Rachel was heading towards the airport for the last time, her taxi was heading west. The Airport is east.
When Eleanor plays mahjong with Rachel, she is handed the dice, which means she is the 'dealer'. She rolls a 10 and starts taking tiles from the stack in front of herself. However, with a roll of 10, the tiles should be drawn starting at the woman to Eleanor's right.
When Oliver is walking with Rachel and Peik Lin at Ah Ma's party, he says something like "look who forgot to wear a bra!", when Rachel obviously does not have a bra on either.
After Rachel spills wine on Nick, Peik Lynn comes in and announces that Rachel thought Ah Ma was the cook. What really happened was Rachel thought Nick's old nanny was Ah Ma.
When Nick is talking to his family about Rachel, he mentions that she teaches millennials. While Nick and Rachel's ages are never explicitly mentioned, we can guess by the 1995 flashback that Nick at least is of the age range generally accepted to be a millennial (early 1980s to mid-1990s). Nick and Rachel seem to be near the same age, making both of them millennials. Unless Rachel is only teaching graduate students, her students would be firmly placed in the Generation Z age range.