WordPress Post save broken with Safari on iPhone/iPad

With Jetpack enabled, any self-hosted WordPress site gets stuck "saving" the post in Safari on iPhone and iPad.

1. 100 saves on Edge, Windows 11 = no problem
2. 10 saves on Safari on iPhone/iPad = gets stuck on "saving" 5-6/10 times

Same with any other browser (eg Firefox) on iOS/iPadOS. The problem disappears if Jetpack is disabled. I don't have a mac I can test with.

Also reported via feedback hub.