Please locate your Analysis server, right click on Fact and Fac2 cube and process. You do not need to Process WB. However you do not need to process manually if have done Full Opt.
What is SP you are using, one of such issue was fixed in SP7 and later versions. However read below note on this :
1696862 - BPC10 Changes in hierarchy cause data in base level members not to be aggregated in the parent
Also, can you check if your issue pertains to only few Parents or you are not seeing nos to any parent.
Thanks,
Rohit Sharma