"Weak memory", as used in this question, refers to the inability to retrieve a memory that a person otherwise knows he has memorized earlier. An example of this is some fact snippet that the individual memorized as part of a training exercise 2 weeks earlier.
Is there scientific consensus for the cause of this type of weak memory? Or is the consensus that there are multiple causes?
Is it possible that this type of weak memory is caused by interference between various signals in the brain, or what does the known evidence say (if anything)?