We have Minecraft for the Nintendo Switch, there are a very small number of worlds (4) with 3 of them being only 10-20mb in size. Our main world is at 400mb and while exploring yesterday to look for new biomes the game closed and we were given a message about there not being enough space and to maybe delete some old worlds. Our Switch currently has 17GB free on the system itself and 71GB free on the SD card so we're not sure how space can be an issue, especially with the world size only being 400mb. 

Any help would be greatly appreciated.