Thanks for the prompt reply.
Could you please resend the original video? The artifacts are clearly visible, but the YT compression is killing any details. The best option would be contacting us here with the video attached:
https://support.chaos.com/hc/en-us/requests/new
Will this weTransfer link be ok? I’ve requested a Chaos password recovery but it’s taking ages to come through.
https://we.tl/t-CnsZjtsCnu
First of all, with this kind of fly-through animation and only some minor moving objects like the 3D people, you do not need to recalculate the cache for each frame. The solution is to save the cache file only once and then reuse it for the whole sequence. You can learn more here: https://support.chaos.com/hc/en-us/articles/4528617365649
For this I calculated every 5th. Maybe I’ve misunderstood the whole caching process for years. What we do is normally cache every 15-25 (depending on the job) but with animated objects we go lower.
We also do cache’s per shot (we generally do cut shots)
Secondly, I would advise using the UHD Cache instead of the 4K Cache. While they are generally both working fine, the 4K Cache is still experimental, so it may fail in some scenarios (this seems to be the case here…).
Great… Fantastic 
If it is the case that it’s because I’ve used 4K, I’ll stick with UHD until it’s considered stable.
For this job there’s only 3 shots and they’re long & winding. The caching process was taking ages… I put it down to quite a few Anima characters (a lot 4D ones).
So, I split the job into 11 shots.
This’ll hopefully make it easier to just work on the troublesome shots… I don’t know anymore.

And lastly, at least some of the flickering (especially by the end of the animation) looked like something caused by overlapping polygons (Z-fighting). The solution to this would be inspecting the scene and making sure that the models are set up correctly.
The white parts that flicker seem to be fine. I’ve selected a face and deleted it. Nothing intersecting. I’ve made sure I haven’t been a plonker and got a duplicate building overlapping. I’ve also selected one of the white balconies detached it - a cube… and it has 8 vertices.
Thanks