Students with a gap between qualifications routinely assume their case is weak, and the assumption produces exactly the behaviour that makes it weak: they leave the gap out of the SOP, hope it goes unnoticed, and then freeze when it is raised in the interview.
Nothing in any major destination's rules penalises a gap as such. What gets penalised is a timeline the reader cannot account for — because an unaccounted year invites the reader to invent an explanation, and the invented one is never generous.
Frame it once, then carry it everywhere
Work experience, family responsibility, retakes, health, self-study, or preparation for a test you did not initially pass — all of these are ordinary human reasons that read perfectly well when stated plainly and evidenced where possible.
The requirement is consistency. The explanation in your SOP, the dates on your CV, and your answer in the interview must be the same explanation. Applicants get caught not by having a gap, but by giving three slightly different accounts of it.
One confident sentence
In a credibility or consular interview, the correct response to a question about your gap is short, factual, and unembarrassed. Long, defensive answers signal that you consider it a problem — and the officer takes the cue.
Prepare that sentence. Say it out loud until it is boring. Boring is the goal.