What substrate are you using? And what are you using for the drainage layer?
There are two scenarios:
1) You are overwatering the system so the drainage layer filled up and is now spilling into the soil. If this is the case, you need to cut back on watering significantly. The soil can go anaerobic and be a breeding ground for bad bacteria.
2) The soil/substrate you are using does not evenly distribute the water (e.g. via peat moss), so once the water the topsoil, it just puddles up instead of getting distributed. Once the water distributes, any excess water drains into your drainage layer. If this is the case, change your soil to an ABG mix or ABG mix-like substrate. You can even make your own, or buy cheaper substitutes and add some ingredients for better drainage.
Puddling water is not good regardless. If you answer my first two questions, I can better help you out. From the pictures, it looks like you are just using regular soil. Once the soil becomes over-saturated, it almost acts like clay. I would change the soil to a substrate (as ABG mix actually isn't soil).
As for watering/misting the enclosure, you will need to more careful. It can be a delicate balancing act. Since you have a garbage bag holding in the drainage layer and substrate, it becomes much harder to tell how much water the system needs. You can't see the buildup of water the same way that you would in a glass terrarium or a screen enclosure with a clear drainage/substrate holder.
For chameleons, it is tempting to blast them with water, but they really don't need as much water as what is advertised. If you spray the enclosure in the morning, you only need to spray until the leaves get wet and are holding water droplets (if the substrate looks dry, you can mist for a bit longer). Any more than that is just excessive. The substrate should do a good job at keeping up the humidity, so brief watering sessions are all you need. Running the water for longer results in the water going straight to the drainage layer. This is water that can no longer be utilized. Having some water in the drainage layer is perfectly fine, even beneficial for your plants' roots, but you don't want a drainage layer with a lot of water.
My jackson's chameleon sleeps in a spot where he doesn't get hit by the mist. Once the mister stops and he starts his day, he begins to lap up the water off the leaves. He is perfectly happy and healthy. I always check his eyes to make sure they aren't sunken in, and I also check his urates. Watering until the leaves just begin to start dripping water is fine. Because that is all the water they really need.
If you find that the humidity is getting too low, causing you to mist more frequently to get that humidity up, you can always try covering the front of the screen cage (with the exception of the bottom maintenance door) with window insulation shrink film, a clear shower curtain, or marine vinyl. However, if you keep the substrate a nice moist consistency that isn't sopping wet every time you mist, that should be sufficient for a chameleon. They can choose their preferred gradient and will probably opt to sleep closer to the substrate on some branches to get a higher nighttime humidity.
Also looking at your pictures, you should completely block off the sides. You will find that you will need to mist less frequently. You can always try to mist more frequently at short intervals instead of misting less frequently at longer intervals. The longer the mist session, the more likely that you will get water building up in your drainage layer.
You can also listen to this podcast episode with Michael Nash: . It's a great episode on bioactive setups. He doesn't use a drainage layer, but he is also more experienced. I would recommend a drainage layer, especially if you are just learning.
Apologies for the long answer. I definitely need to work on short and concise lol