Change background image using key-frames, background image is white after switching to other app and go back to browser

Question

I'm using key frames to change the background image of a div, so far so good, the images changes as I expect.

However, on iOS devices, when I switch to other app and go back to browser, the background images disappeared.

iOS version: 14+

Tested on iPhone 7, 8, 11.

Browser tested: Chrome, Safari.

This does not happen on Android.

You can check this fiddle and test for yourself.

Any help appreciated!