error on recalculate project

thnaks for the description.
I recorded Ticket #1154, and will try and reproduce thanks to your description of tests case.
thanks for reporting.

After first analysis, it seems to be some dependency loop issue.
When moving group of activities, it may happen that control of dependency loop does not correctly trigger error on sub-activity, to forbid the move.
So you may get a dependency loop that will generate the error you're facing when calculating planning.
I'll investigate to :
- avoid dependency loop
- detect these loop on planning calculation to avoid error message