Ah, took you guys quite a while to realise that, eh? 

So, what actually happened?
- Most of China's HD channels, such as CCTV 4, Hunan TV, Zhejiang TV, Dragon TV, is being transmitted from Chinasat 6A satellite (125°E).
- Those "same time as China" variety shows you see on Quan Jia HD and SHX, Astro previously receives it via Chinasat 6A satellite (C band). 
- However in late December 2021, Chinasat announces that Chinasat 6A satellite experiences some anomaly, hence they decided to retire that satellite / don't want to take risks to continue using that satellite.
- Chinasat uses its other satellite named Chinasat 6C, which originally operates at 130°E, and it moves to 125°E to take over Chinasat 6A satellite operations. Therefore, almost all of its existing channels on Chinasat 6A continues to transmit on the Chinasat 6C satellite on the same orbital position of 125°E.
- But the thing with Chinasat 6C satellite is, its C band satellite coverage mainly covers China and Australia/New Zealand only. From the coverage footprint map, it appears that the satellite wasn't primarily meant to provide coverage for SEA countries including Malaysia.
  Chinasat 6C satellite's C band coverage

- It is safe to say that Chinasat 6C satellite coverage does not cover Malaysia at all, therefore Malaysia can no longer receive the majority of China's HD channels via C band like CCTV 4, Hunan TV, Zhejiang TV, Dragon TV and others via C band anymore.
- This not only affects Astro but even for those who *ehem* secretly install 6ft dish and aims at Chinasat 6A to receive China channels ones, they are affected too *cough* *cough*...
- However, the best alternative available is, you can still receive those same China channels from another satellite, Chinasat 6B (115°E), but almost all of them is in MPEG-2 SD channels, which has been in broadcast for decades.
- The C band satellite coverage of Chinasat 6B (and also the 6A) covers entire Asia, Eastern Europe, Australia/NZ... So definitely Malaysia can receive it, and that's why you see CCTV 4 channel on Astro in SD quality now.
  Chinasat 6B satellite's C band coverage

I watch CH335 now, the video quality seems okay to me... 
Astro still broadcasts CH335 (CCTV 4) channel in HD quality. But since Chinasat 6C replaces Chinasat 6A, therefore Astro had (no other better choice but) to receive CCTV 4 channel from the Chinasat 6B satellite, which is in MPEG-2 SD quality, VBR around 2-4Mbps.
As a result, now it's like you're watching an upscaled SD quality of CCTV 4 channel.
That may explains why you feel like the picture quality is still "somewhat okay" but not as sharp as previous. Or maybe, you didn't even bother to realise it until you read this article. 
Or, for those who is attentive enough, you would have noticed that the "高清" indicator on top right corner of the screen on CCTV 4 channel, has disappeared since 2 weeks ago 🤣
However during commercial breaks when Astro slots in advertisements, you will notice that those ads are in Full HD quality, But once it resumes back to CCTV 4 regular programming, the quality will be back in SD again.

Conclusion
Whether is this permanent or not, that depends on CCTV themselves whether would they consider re-transmit/relay CCTV 4 HD channel to other satellites that offer global coverage instead of just Chinasat 6C like now.
Otherwise, perhaps they might consider providing the HD channel through fibre IPTV to the pay TV providers? That might involve some additional costs...?   
Apart from that, Astro would just obtain the "original copy" of the particular China programme (without channel logo all those) and then airs it as usual on Astro QJ or SHX, be it a live or recorded programme.
But still, that's probably best effort basis and no obligations involved.

Don't need to call Astro to complain. It's not that they can do much about it also.
If they can provide CCTV 4 channel in HD quality again just like the usual days, they would've done it long ago, don't you think? 

oh my god so now we watch this china channel in time 1 month now this china channel still the same in SD channel we don't stupid use buy money in SD channel now i don't trust this rubbish astro service time now i done