My worms never climb up the sides of my bin, but then my bin is huge and drains really well.

How much drainage does the bin have and how wet is yhe medium?

I've heard that they try and get out if conditions are acidic. That occasionally happens in my bin. I get some dried eggshells and blitz them to a powder and sprinkle them on the top and that seems to fix it.
The Calcium Carbonate neutralises any excess acid.

Bin is not wet. Maybe even too dry. They seem to be crawling the sides, not necessarily leaving the bin. Drainage holes in the bottom, no standing water anywhere.

I'll add some egg shells right now.

What would help is making the soil underneath the bin more soft, so they can move into the soil from the bin to protect them from excess water. I would dig up the soil under the bin to make sure it is not hard and add a lot of compost to that soil. But, sometimes some of red worms like to hang on the sides, but that does not mean they are all leaving unless it's something really like all of them are, just a couple does not mean total disaster.

I've read that worms may do this initially in new set ups. Make sure not too wet/dry, and I've read exposing the box to light from the top will scare them back underground. They only wander in dark it seems.

Yeah, the light helped. They went down within 10 minutes.

Soil is not compact. Is coir and shredded newspaper.

Hi Tomato,
You'll get a lot of help at the vermicomposting site as well!

Coir and Newspaper is quite acid loving, I reckon some lime and brown sugar should see them happier and want to stay at home ;-)

Oh that could explain, if its not food scraps and leaves and that sort of thing, why the worms are not happy. Have you added some garden soil? The may like some of that.

Yeah, my base was shredded newspaper, some maple leaves, and coir. I added the worms and then 24 hours later, added coffee grounds and veggie scraps. Then all hell broke loose and they were all along the lid when I opened it up. They've since gone down and are munching away, and if I leave the lid on, about 50 or so will make their way to the top again.

When I start a new bin, I always have a lot of compost that is not yet ready so I have like a good matrix of stuff that looks like dirt. Worms like to be covered up with a good matrix. Did you know sun light can kill them? If you see a worm on the ground try to bury him, but it likely already too late as the light has killed him, even if he is still moving. They like a cool dark sort of matrix, I add coffee grounds and ground up bagged wood when they is not enough to keep things well covered up and it makes better compost and you have more compost also.

Way late to the party but it doesn't sound like anything was wrong with your bin. Tubs hold moisture, worms like moisture. Sides and top are wet and they go for a stroll(?)

If it was acidic they wouldn't have been on the sides, they would have been on your floor.