[Wuthering Waves] Cross-save not syncing — anyone else?

Finally worked this out, so here is the write-up I wish I had found. Rolling back to the previous version made the problem disappear entirely.

It seems to depend heavily on region, which nobody mentions anywhere. Will update the post if I find a cleaner solution.

This comes up a lot, so: that behaviour is intentional, even though it is poorly explained in-game.

Worth a shot before anything drastic.

Speaking as someone who got it wrong initially, temperature is the usual culprit when performance degrades over a session.

This comes up a lot, so: the trick is to change one thing at a time and actually note the result before touching anything else.

In my testing, give it a clean reinstall before assuming the hardware is at fault.