How this works
Currently we have parallax X and Y parameters that control how far away a layer feels. Currently it's only taken into account for camera moving sideways.
This pull request makes ...
Btw, there's a video in the PR that shows it working on existing maps (without changes to them): https://m.youtube.com/watch?v=W7eXQN0gRFI.
The client side option to toggle the feature is no longer there though. In order to disable it, you'd have to set Para Zoom to 0 (infinite distance) on a layer group (if it had non-zero Para X/Y, otherwise it will be 0 by default).(edited)
I had pretty similar issue few years ago, problem was in my router, but i cant be sure if thats your case, if you can temporarily replace it or test it, I'd recommend you to do it(edited)