Can you show us your process bpmn2?
>> Tasks assigned used to work, but suddenly it stopped working. << -- something probably changed then
I see your point, but at least I should see an error somewhere. Also I made few changes but, it does not even get to new changes.
Maybe the exceptions are being swallowed for some reason. Typically you should see some indication of the failure in your server.log. If you pastebin your bpmn2 we can help with debugging if needed.