I think I've fixed it...
I ran the support tool "Something isn't working correctly" and it disabled a few things. I reenabled them one after the other and found that the problem came from the theme, in globalTemplate.
After reverting globalTemplate to default, I noticed that it fixed the problem and also that there were differences in the code in a few places in the file, for instance :
Before :
</footer>
{{if !\in_array('ipsLayout_minimal', \IPS\Output::i()->bodyClasses )}}{template="mobileNavigation" if="theme.responsive" app="core" group="global" params=""}{{endif}}
{template="guestTermsBar" if="!\IPS\Member::loggedIn()->member_id and \IPS\Settings::i()->guest_terms_bar" app="core" group="global" params="base64_encode( \IPS\Settings::i()->base_url )"}
{template="includeJS" if="theme.js_include == 'footer'" app="core" group="global" location="global" params=""}
{template="viglink" if="settings.viglink_enabled" app="core" group="global" params=""}
{template="metaTagEditor" if="isset( $_SESSION['live_meta_tags'] ) and $_SESSION['live_meta_tags'] and member.isAdmin()" app="core" group="global" params=""}
<!--ipsQueryLog-->
<!--ipsCachingLog-->
After :
</footer>
{template="mobileNavigation" if="theme.responsive" app="core" group="global" params=""}
{template="guestTermsBar" if="!\IPS\Member::loggedIn()->member_id and \IPS\Settings::i()->guest_terms_bar" app="core" group="global" params="base64_encode( \IPS\Settings::i()->base_url )"}
{template="includeJS" if="theme.js_include == 'footer'" app="core" group="global" location="global" params=""}
{template="viglink" if="settings.viglink_enabled" app="core" group="global" params=""}
{template="metaTagEditor" if="isset( $_SESSION['live_meta_tags'] ) and $_SESSION['live_meta_tags'] and member.isAdmin()" app="core" group="global" params=""}
{{endif}}
<!--ipsQueryLog-->
<!--ipsCachingLog-->
Does it mean the upgrade was not complete ?...
Thank you. 🙂