You must have in your database some line of planningelement with refType / RefId referencing a deleted activity.
Could you check this, and confirm thos analysis.
Could you also identified how these activities where deleted ? Possibly these are activities deleted through parent deletion.

I recorded Ticket #1419 to investigate.

I'll check the database. I'll have to ask our IT personnel to give these info.
About the deletion procedures:

At first, I started deleting each activity separetely. Id did that for all child activities below Parent Activity 03 (according to the structured shown in the previous post).
Then I started deleting the activities through parent deletion.

PS: Althought in the structured shown in the previous post I had only 03 Parent Activities, in real life I had 04 parent activities, and deleted 03 parent activities, which matches with the number of tasks appearing in the planning screen.

Not sure if it is related or not, but when you delete a child activity which has an Assignment, first you have to delete the assignment then de activity (it doesn't have cascade deletion). But, when you delete a Parent activity, even if the child activities have Assignments, the deletion occurs in cascade mode and there's not system message requesting to first delete the Assignments (similar to child activity deletion).

Thanks.

Hi,
I get the result from planningelement table and found 04 records which doesn't exist anymore in the activity table.

I'll have to do is to delete those 04 records in planningelement table, correct? Is there any other table which needs maintenance?

Kind Regards,

I'll have to do is to delete those 04 records in planningelement table, correct?

Yes

Is there any other table which needs maintenance?

No, no other.

A patch will soon be proposed.

Thank you very much indeed. Kind regards.