The "save image" button is missing from the share sheet on iOS or I can only save an image once via the share sheet once on iOS

Unfortunately, this is a regression of Safari on iOS 16: 255544 – Web Share API Level 2 missing "Save Image" button on iOS 16. You can see the same behaviors in the official web share demo: Web Share Test. You might consider displaying text like “Press and hold photo to save” on iOS like this sample project: Capture Photo | 8th Wall | 8th Wall. If you want to hide the share button/display text only on iOS, you can add some additional logic:

AFRAME.registerComponent('ios-share', {
  init() {
    const onxrloaded = () => {
      if (XR8.XrDevice.deviceEstimate().os === 'iOS') {
        document.getElementById('actionButton').style.display = 'none'
      }
    }
    window.XR8 ? onxrloaded() : window.addEventListener('xrloaded', onxrloaded)
  },
})