1. Can you reproduce this?
Yes it happened again on another service, tasks show UNSUCCESSFUL execution but continues to next task in a job and it should not allow that. Also statuses show everything RUNNING when in reality only one task is running.
2. Do you have any special "Flow" on the first Task or Conditions on second?
No special FLOW on anything other than Notifications to go out when the Job Starts or Ends.
The only way to correct this is to stop the service and restart. I've seen this in earlier versions but it seems much worse in the newest version.