This issue appear randomly, changing the browser seem to resolve the bug
Fatal error: Uncaught exception 'Exception' with message 'String could not be parsed as XML' in /var/www/movim/lib/Moxl/MoxlAPI.php on line 342 Exception: String could not be parsed as XML in /var/www/movim/lib/Moxl/MoxlAPI.php on line 342 Call Stack: 0.0014 637896 1. {main}() /var/www/movim/index.php:0 0.0507 2283936 2. ControllerBase->handle() /var/www/movim/index.php:52 0.0508 2293368 3. ControllerBase->run_req() /var/www/movim/app/controllers/ControllerBase.php:48 0.0509 2294000 4. call_user_func() /var/www/movim/app/controllers/ControllerBase.php:83 0.0509 2294000 5. ControllerMain->disconnect() /var/www/movim/app/controllers/ControllerBase.php:0 0.0509 2295904 6. User->desauth() /var/www/movim/app/controllers/ControllerMain.php:389 0.0520 2303800 7. moxl\PresenceUnavaiable->request() /var/www/movim/system/User.php:71 0.0836 2303800 8. moxl\presenceUnavaiable() /var/www/movim/lib/Moxl/xec/action/presence/PresenceUnavaiable.php:32 0.0837 2304416 9. moxl\request() /var/www/movim/lib/Moxl/stanza/base/Presence.php:53 0.1040 2310032 10. moxl\handle() /var/www/movim/lib/Moxl/MoxlAPI.php:294 0.1041 2311280 11. SimpleXMLElement->__construct() /var/www/movim/lib/Moxl/MoxlAPI.php:342
I suspect the Session handling class
Also experimented sometimes, not sure about the error (not checked the logs)