this bug appears on Bordeaux 3: https://issues.anyware-tech.com/browse/UBIII-580
How to reproduce it:

• Open a page
• Edit it
• Insert a Flash from the ressouces explorer
• Save

What happens

• the flash is not displayed

Required behavior:

• the flash is displayed

At this time we have in the headers
Content-Disposition attachment

It seems to be the source of the problem.

We did a hack in /home/cms/Ametys_CMS/application/cms/modules/resources/sitemap.xmap
We removed:
<map:act type="set-header">
<map:parameter name="Content-Disposition" value="attachment"/>
</map:act>
And the flash was played correctly