@chinesegeorge, thank you for posting this. Using my new logs, I was able to follow this up in exactly. I can see that your browser has first uploaded 12 (Bugatti) pictures and than saved the forum post. This was executed without a glitch and altogether in just under 3 seconds, which is great.
After that you have successfully uploaded ca.10 pictures which processed fine. But the server has no trace of "Save" request on the post. Not that it went wrong - it was never received/processed server-side.
The message that appeared in your browser does not come from iModeler, but from the Safari browser.
The "Cannot Parse Response" error in Safari, especially on iOS, is often seen when the server sends an unexpected response format or when there's a network interruption. As there was no response from the server, network interruption or patchy communications of some kind appears rather likely in this case.
I have found this read about possible garble in Safari that may be causing this. Not sure how relevant this is, but might be worth checking.
https://appuals.com/cannot-parse-response-safari/
I will, however, double-check the Javascript behind the "Save" button to see how it sends/handles save requests. For sure, it should not simply close the form unless the save operation has been confirmed as successful.