The current version of ST seems not to be compatible with SMW 4.x. If you enable it, the following error shows:
[4f2023c3f2d606fb4f7f4520] /wiki/ Error from line 66 of ../extensions/SemanticTasks/SemanticTasks.php: Class 'ST\Assignees' not found
Backtrace:
#0 /var/www/km-a/1.35.6/includes/Setup.php(806): SemanticTasks::onExtensionFunction()
#1 /var/www/km-a/1.35.6/includes/WebStart.php(89): require_once(string)
#2 /var/www/km-a/1.35.6/index.php(44): require(string)
#3 {main}
Issue
The current version of ST seems not to be compatible with SMW 4.x. If you enable it, the following error shows: