Move project to subproject, WBS of activities not update?

Hi,

I have a question about the WBS calculation. I created two projects A (wbs: 2) & B (wbs: 3) and have some activities (wbs 3.1, 3.2) assigned under B project. Then I changed B project to be a sub-project of A. The project wbs of B is changed to 2.1
But I found the wbs of the activities of project B are not updated.

I checked with your demo system that your wbs calculation is working well. I tried to do some diff for the Project.php & PlanningElement.php with V1.5.5 & V2.3.0 in 'save' function but can't find differences/modification for WBS calculation.

I am using V1.5.5 with some custom modification that I can't upgrade to the latest version of system.
Can you help to point out which files/functions are modified for this WBS re-calculation?
Thanks a lot.

Best Regards,
Selina