How might spaced repetition memory systems intervene when the student struggles with material? There are many possibilities, but the choice must depend on the nature of the reader’s struggles.
If the reader is simply failing to remember something which they’re meant to memorize, there’s no need for extensive interventions: knowledge of correct answer plus more practice should be enough.
If the reader’s inability to answer reflects holes in their conceptual understanding, explanation and elaboration might be best.
If the reader struggles with procedural knowledge, it may not be because they’ve failed to memorize the procedure. Instead, it may be that they’ve not internalized when, where, how, and why the procedure is to be applied.
If the reader explicitly believes something that’s incorrect, more elaborate diagnosis and intercession might be necessary.