You need more practice when the idea is understood but not yet reliable; you need a better explanation when the idea itself is still unclear. A learner who understands can usually explain the method, recognise when to use it, and correct mistakes after feedback, even if speed and accuracy are not yet stable.
A better explanation is needed when the learner memorises steps without understanding why they work, cannot identify the first move on a slightly different question, or repeatedly guesses despite substantial practice. Repetition cannot stabilise a model that was never properly built. Clarify the concept first; then practise until retrieval and execution become dependable.
Use the Diagnostics & Recovery Hub to decide which kind of failure you are seeing, then move to the relevant subject route from the eduKateSG Learning Hubs.