Thank you so much for taking the time to look into it,
richard2480
The test user (w.bery) completed, downloading one image that used to fail, but some other users I tried next (having image posts) fail in a similar manner.
Here, the first user has many photos and they all completed without a hitch. The second user has a history json with no new images since the last DL 3 days ago, only videos - so they also completed. However, redownloading from scratch leads to the same error with images as the third user here below.
(Also, that fallback is something new - now idea what it means, but I can browse/scroll TikTok logged-in or not without any problems and can manually download from TikWM using something like BatchURL just fine, I don't feel rate-limited). Maybe the URLs are different somehow and that's why it fails?