Dude, I thought your camera can't have filters installed. Did I just misunderstand or forgot? great news anyway!
And well, if the filter is not perfectly placed, maybe it will just reduce the glare but not at best. The actually if it's really placed in the perfectly bad position, it can actually make it even worst, but you must really have bad luck.
In most cases if you keep it in the "top" position you can't go totally wrong
