The compostable liner although it looks and feels like plastic its not, it is made from corn starch which allows it to breathe.

The Brown bin even with vent holes which some bins have still does not allow sufficient air in, so the compostable liner is doing its job by breathing but the moist air from it is then trapped, and so the bins walls get damp and the liner sticks to them.

This is why the Aerated Kitchen caddy from Brown Bin Rescue does not create any foul odours, as it allows the corn starch liner to breathe.