Thank you Joffm,
Can you test it twice.
It seem to work the fisrt time, then stop working after 2 or 3 try.
Really strange.

Joffm, what version of Chrome are you running? It worked for me before the update (83.0.4103.106 - same as Tpartner).

With the lastest Chrome (83.0.4103.116) it didn't work anymore.

Now I tried the link even in an incognito window and the same result: Not working.

I created a bug report
bugs.limesurvey.org/view.php?id=16415

holch wrote: J It worked for me before the update (83.0.4103.106 - same as Tpartner).
With the lastest Chrome (83.0.4103.116) it didn't work anymore.

Seems really an issue in Chrome , not in LimeSurvey …

Can you activate log and return all you can.

Network for example
(i can check myself : no issue on Linux with same Chrome version)

Here are the Console and Network events

For all checker : test this update : github.com/LimeSurvey/LimeSurvey/pull/1445/files
Remind to reset asset .

How do I "reset asset" ?

You can refresh the assets cache via Global Settings -> General -> Clear asset cache

Adding theses lines
// For Chrome
iframe.src == "javascript:false" ||
iframe.src == "javascript:false;" ||
it breaks the upload (tested on Windows Chrome and Firefox, Ubuntu Chrome and Firefox, Mac Firefox)

stays on sending. .. ... .... .....
See gif attached

Commenting this line make it work again.
// iframe.setAttribute('srcdoc', this._settings.action);

Do you think I can change this on my production server (as this project is pretty urgent)?

No idea since i can reproduce the issue on *nux …