I believe you need to ajust the “size” of the camera, right below Projection type. Instead of 15, raise this. Check the scene preview when you select the camera (double click it in the Hierachy) and see how large an area it covers.
To all facing the same problem, this is the solution:
Forces SpriteManager to recalculate the bounding volume of the mesh in the next LateUpdate(). This is important to do periodically to ensure that Unity’s visibility culling can cull the mesh when not visible, and also so that the mesh is not culled erroneously when it is visible. If your objects all remain pretty much in the same area, it is less important to call this frequently. However, if your objects move around quite a bit and the bounds are not recalculated, it is very easy for them to extend beyond the bounds of the previously updated bounding volume, causing Unity to cull the entire mesh based on the earlier boundaries, resulting in parts of your mesh which should be visible to disappear. Performance note: Will cause Unity to recalculate the bounds of the mesh, which can be very performance intensive with a large number of sprites. Consider using ScheduleBoundsUpdate() to keep from recalculating bounds each frame.