My little girl who is 15 months has started climbing the cot at night. What age did you take the side of the cot off? And obviously put a bed guard on.
As soon as they start climbing out! My son was two when he started to climb but I would say whenever they start to climb, the cot has become dangerous and you ought either to take a side off or move them into a bed. We actually bought a day bed with three sides second hand and put a bed guard on the fourth. My son can climb out but can’t roll out in his sleep. We made sure the room was childproof and that we had a stair gate at the top of the stairs for when he gets out of bed and stumbles along to our room in the middle of the night. Good luck!