Survival is more than not getting lost. Every time a group fails a survival check, there is a random list of things that can go wrong. Food spoils much faster in Jumanji, so perhaps someone didn't preserve the food properly and 1d6 days of food goes bad. Water becomes diseased. Tents become damaged and let in weather exposing the group to the risk of being sick.
Survival is more than not getting lost. Every time a group fails a survival check, there is a random list of things that can go wrong. Food spoils much faster in Jumanji, so perhaps someone didn't preserve the food properly and 1d6 days of food goes bad. Water becomes diseased. Tents become damaged and let in weather exposing the group to the risk of being sick.