Hi ,
If the cube directly loaded from PSA then the deltal ogic is different than other flow. means ther is no delte/new/change concept in this load. becuase cube works on additive.
there should be daily delta job , and please note the start time/time stamp, before the job starts in BW, check the no of records in RSA7. once the load is completed then check n PSA. you will find the root cause if the records are missing.