Crawling up the sides is normal as they love to escape. Keep a tight lid on and dont worry about it. I have screen tops on mine and certain times they really want to escape and when I notice more than 1 or 3 on the sides, I turn on a light above the bin and that drives them back under the soil. A friend once told me they mostly do that because they are looking for food or to expand their range. He raised them commercially for years and his beds were huge 4'x8'x3' deep. He told me about the light and it does work but I just make sure I have tight fitting lids and dont worry about it.

