We have archive.php running every hour for around 700 sites. It usually runs fine without error. Except that every Monday we get errors like this:
SCHEDULED TASKS
Starting Scheduled tasks...
ERROR: Got invalid response from API request: http://OURDOMAIN/index.php?module=API&method=CoreAdminHome.runScheduledTasks&format=csv&convertToUnicode=0&token_auth=OURTOKEN&trigger=archivephp. Response was '<div style='word-wrap: break-word; border: 3px solid red; padding:4px; width:70%; background-color:#FFFF96;'>
<strong>There is an error. Please report the message (Piwik 1.12)
and full backtrace in the <a href='?module=Proxy&action=redirect&url=http://forum.piwik.org' target='_blank'>Piwik forums</a> (please do a Search first as it might have been reported already!).<br /><br/>
Notice:</strong> <i>Undefined variable: message</i> in <b>/var/www/html/piwik/plugins/PDFReports/PDFReports.php</b> on line <b>347</b>
<br /><br />Backtrace --><div style="font-family:Courier;font-size:10pt"><br />
#0 Piwik_ErrorHandler(...) called at [/var/www/html/piwik/plugins/PDFReports/PDFReports.php:347]<br />
#1 Piwik_PDFReports->sendReport(...) called at [:]<br />
#2 call_user_func_array(...) called at [/var/www/html/piwik/libs/Event/Dispatcher.php:284]<br />
#3 Event_Dispatcher->postNotification(...) called at [/var/www/html/piwik/core/PluginsManager.php:674]<br />
#4 Piwik_PostEvent(...) called at [/var/www/html/piwik/plugins/PDFReports/API.php:535]<br />
#5 Piwik_PDFReports_API->sendReport(...) called at [:]<br />
#6 call_user_func(...) called at [/var/www/html/piwik/core/TaskScheduler.php:157]<br />
#7 Piwik_TaskScheduler::executeTask(...) called at [/var/www/html/piwik/core/TaskScheduler.php:72]<br />
#8 Piwik_TaskScheduler::runTasks(...) called at [/var/www/html/piwik/plugins/CoreAdminHome/API.php:38]<br />
#9 Piwik_CoreAdminHome_API->runScheduledTasks(...) called at [:]<br />
#10 call_user_func_array(...) called at [/var/www/html/piwik/core/API/Proxy.php:188]<br />
#11 Piwik_API_Proxy->call(...) called at [/var/www/html/piwik/core/API/Request.php:145]<br />
#12 Piwik_API_Request->process(...) called at [/var/www/html/piwik/plugins/API/Controller.php:25]<br />
#13 Piwik_API_Controller->index(...) called at [:]<br />
#14 call_user_func_array(...) called at [/var/www/html/piwik/core/FrontController.php:125]<br />
#15 Piwik_FrontController->dispatch(...) called at [/var/www/html/piwik/index.php:47]</div><br />
</pre></div><br />task,output
Piwik_PDFReports_API.sendReport_425,Time elapsed: 1.124s'
Is there a known issue with SCHEDULED TASKS phase of archiving? Is there a suggested fix?