TYPO3 Core

This bug happens if you are doing a copy of task directly in database.

The new record in database will have a new UID but serialized Task object will still have the old UID.
When you try to do an update from TYPO3 Backend module, the old Task is updated when you edit the new one.

One solution would be to update Task UID.

In version 4.5/4.7:
(typo3/sysext/scheduler/class.tx_scheduler.php:300)

$task = unserialize($row['serialized_task_object']);
+ $task->setTaskUid($row['uid']);

(typo3/sysext/scheduler/class.tx_scheduler.php:365)

$task = unserialize($row['serialized_task_object']);
+ $task->setTaskUid($row['uid']);

(typo3/sysext/scheduler/class.tx_scheduler_module.php:611)

$task = unserialize($taskRecord['serialized_task_object']);
+ $task->setTaskUid($taskRecord['uid']);

(typo3/sysext/scheduler/class.tx_scheduler_module.php:1047)

$task = unserialize($schedulerRecord['serialized_task_object']);
+ $task->setTaskUid($schedulerRecord['uid']);

(typo3/sysext/scheduler/class.tx_scheduler_module.php:1231)

$task = unserialize($taskRecord['serialized_task_object']);
+ $task->setTaskUid($taskRecord['uid']);

In version 6.0/6.1:
(typo3/sysext/scheduler/Classes/Controller/SchedulerModuleController.php:557)

$task = unserialize($taskRecord['serialized_task_object']);
+ $task->setTaskUid($taskRecord['uid']);

(typo3/sysext/scheduler/Classes/Controller/SchedulerModuleController.php:945)

$task = unserialize($schedulerRecord['serialized_task_object']);
+ $task->setTaskUid($schedulerRecord['uid']);

(typo3/sysext/scheduler/Classes/Controller/SchedulerModuleController.php:1110)

$task = unserialize($taskRecord['serialized_task_object']);
+ $task->setTaskUid($taskRecord['uid']);

(typo3/sysext/scheduler/Classes/Scheduler.php:108)

$task = unserialize($row['serialized_task_object']);
+ $task->setTaskUid($row['uid']);

(typo3/sysext/scheduler/Classes/Scheduler.php:277)

$task = unserialize($row['serialized_task_object']);
+ $task->setTaskUid($row['uid']);

(typo3/sysext/scheduler/Classes/Scheduler.php:337)

$task = unserialize($row['serialized_task_object']);
+ $task->setTaskUid($row['uid']);