I'm trying to create the gap between the top and bottom casings and the bevel is not generating the same way. It's only on next to the battery casing that it's messing up. I've made sure there's nothing else selected than the line.
Try the first two things that are most common, you have double vertices,so select everything with A and then M to merge by distance. And see if your scale is applied. Also check your normals are consistence.