Sometimes despite pre assess and careful planning using the Progress on Topic the teacher will realise that they have taught the learner something which is taking too much feedback and practice time and the learner doesn't look like they will master that piece of learning soon.
The teacher should be pleased with themselves for doing excellent assessment for learning and recognising this. The teacher can remove the layer from the retrieval practice cycle by deciding the layer is best learned later.
Without timely practice the best learned later layer would have been quickly forgotten. The teacher should decide that this layer will be removed from the learners' timely practice pool (all the layers the learning is practising) for now, so that the learner can concentrate their efforts on all the other layers. When the teacher thinks the learner is ready the teacher can teach the learner the layer again.