[Mediawiki-l] uncorrect subst behaviour when inside <includeonly>

[Frames Project]

Hello

I am using :

  * MediaWiki: 1.11.0
      * PHP: 5.1.3RC4-dev (cgi-fcgi)
  * MySQL: 5.0.67 

I have a problem with the mixture of <includeonly> and subst in a
Template :

"Template:S" looks like : 
<includeonly>{{subst:A page template}}</includeonly>

and "Template:A page template" looks like
This is the content of a page template

when, after saving, I edit again "Template:S" it now contains : 

<includeonly>This is the content of a page template</includeonly>

The subst has been done, as if <includeonly> has no effect.

This uncorrect behaviour appears and disappears, I do not know why,
there may be some conflict with extensions ?

Could someone help me to understand this very annoying phenomenon ?

The wiki is   http://comprendrelactualite.free.fr/mediawiki/index.php
so, you can look at what is implemented in.

Thanks
Francois Colonna