When you removed a project member it is also removed from binded ugroups. It should not, the next modification in the ugroup (add or remove a member for example) will add again the incorrectly removed user.

Steps to reproduce:
1. Create 2 projects Project1 and Project2
2. Both Project1 and Project2 has project members User1 and User2
3. In Project1 create a new ugroup and add User1 and User2
4. In Project2 create a new ugroup binded to the previously created ugroup in Project1
5. In Project2 remove User2 from project members. User2 is not a member of the ugroup anymore but it is still present in Project1 ugroup.