What should I be working on?

That's a solid performance and , atleast for me, it is hard to detect any major issues or frequent errors. Compared to your first videos I think, that you have improved your body movement while doing clear/smash/drops a lot. Here one of the more experienced users will for sure be more helpful to point out major issues. As a general idea, it would be helpful to play vs stronger opponents, who are able to increase the pressure to enforce more errors.

Still, here are some more (minor) aspects you could revisit if you like:

At 1:07:
First you have a directed split step, the racket foot is alot more forward. Then you do a correction step by moving your left foot forward (farther away from shuttle destination), then you do a lunge. You have trouble to reach the shuttle.
A more neutral split step, followed up by pushing away with your none racket foot in the direction of the shuttle, followed up by a chasse and lunge would increase your reach.

At 1:26:
Similar to the previous, you do a directed split step, do a correction step by moving your left foot forward again away from the shuttle, turn around, take the shuttle. Again you have trouble to get behind the shuttle.
Here again, a more neutral split step, this time push away with your racket foot more powerful to get a better turn around.

At 2.43:
Here you have an improved version of 1:26. You do a neutral split step and you do not need a correction step. If you would do a more powerful pushoff with the racket foot, you would be even better behind the shuttle, leaving you in a more stable position.

A 7:07:
Again, a directed split step where you need a correction step. Additional to this, you smash from an unstable position (too late to get behind the shuttle), from the middle (bad angles ) directly to the middle of opponent (easy to defend), who counters with a fast,short block while you need to recover from an unstable position. Try to play a smash from a more stable position, else it could turn out to be a boomerang.

 

Just a couple of things I'd note:

- long serve racquet foot: as you serve, the foot sometimes comes up before shuttle contact. This is a fault under the rules (the foot much stay in contact with the foot until serve action is completed) and an umpire will pick it up (technically so could your opponent...). @Cheung has me on this one and has reminded me for months. It's actually a surprisingly hard habit to break, give the amount of practice I've put into not doing it.

- round the head movement: footwork is fine, racquet carriage is lazy. Notice how your racquet points almost 30 degrees, even 40 degrees to the forehand side, even though it is clear you want to take a round the head shuttle in your backhand corner. Your racquet should point towards the backhand side, maybe vertically upwards, but not towards FH side. This leads to inconsistency - a trademark feature of this bad habit is that it'll drag your shuttles out the left of the court, as you did in 1:29, simply because you're trying get the shuttle to fly straight, but your racquet is moving at a 30-40 degree angle, diagonally leftwards - at worst it goes out the court, and at best you get a sliced shot.

Overall though your footwork is good, which is aided by your anticipation. Incorporating a more neutral split will allow you to push off later yet more explosively, which will come in handy against deceptive players or at least players you cannot read/anticipate so easily.

 

I think, that the directed split step is the more advanced version, which needs the right portion of anitcipation and the ability to quickly correct it if you need to change direction. You already utilize it in the right way, e.g. at 1:23 you have a directed split step, push away with the racket foot to turn around (no correction step this time), then add a little intermediate jump with your non racket foot (fei bo/flying step ?).

But I think, that a more neutral split step helps to build a more consistent base for your footwork and to reach all 6 corners. You will benefit from very solid foundation in your footwork/technique your whole badminton life long. Higher risk/higher reward movement/anticipation/shots can be build upon this foundation later on.

 

I haven't seen your previous videos until now, but a massive improvement, so good job! A lot of people don't realise how much off court drills/fitness helps on court and never bother to do it.

One thing I notice is that when you play a drop shot from the back of the court, you're a little slow moving back to base. Against those you're currently playing (from what I can tell from the video), it's mostly fine because they're not really putting pressure on you and either lifting or returning a loose net shot. But play someone who can return a tighter net shot, and you'll struggle to get there in time.

 

Bear in mind that quality drop shots don't necessarily mean close to the net. You don't always want to go for tight shots yourself, especially in singles and from right at the back of the court, as their return can be tighter making it counter-effective. Most of the time fast drops are the better choice. If you watch the pros play, you'll see that most of their drop shots are actually landing around the service line or even further back. Also, tight net shots will tend to be slower and arc more, giving your opponent time to step in and kill it.

Keep up the hard work! (When we can! )

 

Your footwork is really solid and you are fast enough, so I think, I'm not really qualified to give you any tips at your level, but one thing got stuck. Your movement to the backhand rearcourt.

It looks always like you are under pressure, you run backward while you already bend your back back and often only a defensive clear is pulled off. I don't really understand why you are not able to get behind it more often, because you seem to be fast enough, here are some timestemps of the first 2 mins, 0:33, 0:39, 1:16, 1:45 , when you bend backward. A problem might be that you didn't utilize your split steps to their full potetial like at 1:45, where you split step, but instead of initiating your movemet backward, you took a sidestep and afterwards you initiate your movement to the back, but at this time already under pressure. Although you miss the little hop with your left foot to get you faster backward while using your bodymomentum to turn to the sides (you hit the shuttle with your body pointing to the net). An other problem might be, that your movement to the backhand rearcourt is just not as explosive as your other movement.

Check this out:

 

I just watched the first minute and one big issue jumps out immediately. When lunging, your balance is completely on the front foot. So much that you even lift the back foot off the floor!

The Balance should stay center, between both feet, giving more stability, while allowing for quick(er) recovery!

To see if your lunge is stable, you can close your eyes and have somebody push you slightly. The shoulders, the hips, .... you should not have to do much to stabilize that.

The question is how do you practice it? And for footwork, the answer always is to shadow. Dry. Boring. Repetitive. But it works.
Focus on the lunge, on stability, when you feel the balance slightly shifting to the forefoot of your front foot, correct it!
Don't start the lunge coming from above, but keep your balance low! Not sure if you know what I'm trying to say here, but when it's pounding when you set your front foot, you're doing it wrong. It should be quiet.

Another hint (and yes, it's getting too much to think about at the same time), the lunge should not be accelerated, but you're slowing down. You want to change the direction... the first step has to be faster for that.

I didn't pay attention to the backcourt footwork yet, because I was waiting for you to just run through the net.