Hello Ahmet
This issue is like a Known Issue sort of thing and was discussed several times in the past. You can have these discussions from this Google page. Though MCI8 inconsistencies is mostly discussed, this is true with many MIS reports. In such case LIS (Logical Info Structure) rebuilding used to be the answer. In Plant maintenance the Infostructures are often rebuilt using OLPM and OLIX. Here perhaps it is done with tcodes OLI5 and OLIX. However you should follow the instructions SAP note referred by Caetano in this context.
Also go through these useful links:
IW39 /MCI8 Report inconsistency --> Sebastian's posts have good information
Cost difference between PM report MCI8 and IW38.
Some general idea on how info structures are rebuilt/updated can be had from these discussions:
Lost of the info structure S026
OLIX and MCIZ reports not updating in Fleet management
Good luck
KJogeswaraRao