Hope you have compared the Equipment lists of both clients (QAS and PRD) through IE05 by querying though Plant section field (L02). And then the list of equipments you get so in PRD display M2 notifications with breakdown tick in IW28.
Also go though this link to verify whether we are missing some thing to build Breakdown statistics in PRD:What are the prerequisite for getting MTTR / MTBR data.
Also you may have to build info structure S070 through OLPM: Issue in MCI7 report - S070 LIS Rebuild . Before going for this step verify the other MIS tcode MCJB for these equipments
These are some possible tools to investigate ans act accordingly. With present information given by you it is difficult to pin-point the reason. Let's hope we arrive at the cause soon.
Good luck
KJogeswaraRao