Probleme Memcached multisite

I have a problem with Mencached on my multisite server (2 Elgg sites). Enabling memcached on my 2 Elgg sites (with different memcache_namespace_prefix) causes some plugins to be disabled on both sites. Have you ever encountered this type of problem?

Debian 11, memcached 1.6.9,  PHP 8.1, Elgg 4.1.3 (2 websites)

I use for one this:

$CONFIG->memcache = true;
$CONFIG->memcache_servers = array ( array('127.0.0.1', 11211), );
$CONFIG->memcache_namespace_prefix = 'exempledeprefix';

and for the other :

$CONFIG->memcache = true;
$CONFIG->memcache_servers = array ( array('127.0.0.1', 11211), );
$CONFIG->memcache_namespace_prefix = 'unautreprefix';