error during the creation of notification

Dear All,

We are facing the error when we are carrying out the transaction EG90

for collective creation of notification for device replacement say out of 1000 equipments 998 notifications were created automatically but for rest two device locations the follwing error comes "internal error during determination of pm plant for device with equipment number xyz

error message EG621 .

I have cheked the master data of the equipments all maintended properly

can you give me some idea what coulld be the problem .

Regards

chan