The key is having air that can move throughout the bin. I have the same issue with the simple bins I create out of 10 gallon totes as I do not add air holes in the bottom they tend to become very wet and almost like mud. However my flow thru bin has none of these issues as the excess water can just trip right out into the bottom and evaporate away.

I would highly recommend corrugated cardboard as that will add some structure and spring to the bin which allows the air to get into some of the nooks.

To help you feel better here is a video with one of my bins where all the worms died due to my neglect and little air movement. So even those with experience run into issues.

My harvest nine times out of ten is soft and crumbly and sphagnum peat is used every time. First soaked in a bucket then sqeezed out by hand to where just a few drops drip out, to this I had a good portion of machine shredded paper. Also I might add a bit of coffee grounds but I dont often add cardboard only on occasion. I do from time to time go into the bin with plastic forked tool and move the mix around to help keep it aerated some plus I can also see what the worms are doing and what condition the bin is in. The amount of kitchen scraps added is in relation to how many worms are in the bin. For people who only start small with 50-100 worms you certainly should not all much food at all vs someone who might have 2000 or more worms your can add a lot more. That might be part of your problem.