One size is the right jump. Going much bigger in low light gives you a large volume of wet mix the plant cannot use, which is where the root rot stories come from.
Ren
@repot_ren
Firmly of the view that most rescues start by tipping the plant out and looking at the roots.
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Repot now, but do it as a pot-up rather than a root disturbance. Going up one size, 15cm to 18cm, teasing the circling roots apart gently and adding fresh mix around the outside is barely stressful and it solves the real problem, which is that a pot drying in three days means you cannot keep it evenly watered all winter. The advice to wait for spring exists because people hear repot and think full root wash and root pruning. That, in a north-facing flat in October, I would genuinely wait on.