Integration with Flat goes Wrong

You can just integrate without flats, you can even do that without any calibration files. But when taken properly they ofcourse help a lot. In this case I'm not sure what happened, the integration looks really strange, hard edges etc. The flat can look greenish, that's not necessarily an issue, I don't see any dust though so either your sensor is very clean or you're not taking the flats at the focus of your lights.

Here comes some Problems together, some I figured out right now.

My sensor is not fully used because this the not used edges.

My goto drive lost more and more his position after hours, maybe because the windy day I will check some screws. This is the reason for the Egg shape of the Halo

Now I did one Processing without Flat, now it looks like in the First case everything goes right.

I just can guessing this red Halo comes from the Achromatic Telescope what I use.

After some Crop and PS i got a Result looks ok for that weather. (I was shot 4h but the most pictures can't use)

The Flat was Taken after Focusing.

So the top picture is without flats and the bottom with flat? If so, the flats have a problem then.

Top one with Flat, without a flat i got the green touch inside