Completely agree with this, some embassies absolutely seem to be rejecting randomly for seemingly no real reason, my Muay Thai trainer told me about this before I applied, she had seen it with many of her students. Most people in here seem to assume that there's always something wrong with the application if you get rejected, that might be the case but it might also be that you got unlucky with the officer. Fully agree its better to apply at an embassy where they do interviews.

Wouldn't recommend Hanoi. A lot of people getting rejected recently despite flawless applications, you can get approved but there's no guarantee even if you qualify. This Muay Thai gym placed Vietnam on the list of countries they are not recommending people to go to: