I recently bought a Tamron SP 150-600mm F/5-6.3 Di VC USD for my Canon T6 camera and I found that it has trouble focusing @ big zooms. The lens will either jump around, focusing on one thing then jump to another and back and forth as though it's confused or it will focus on an object close to what I'm taking a picture of, rendering it a little out of focus and you can't tell until the picture is processed or it just won't focus at all depending on the situation it seems. E.G. Bird in flight 100 meters or less coming toward me, lens @ 500-600mm zoom and it won't focus at all or jumps around in focus. Now I'm taking hits for bad, slightly out of focus pictures and I want that to change. I was told that this is normal behavior with a long focal length. I feel that's probably true, it seems to make sense but can this be confirmed by anyone with the same lens or a professional background in photography. Is my only option to focus manually on such big zooms? It's hard to focus well on moving subjects, especially when you only have a few seconds or less to do it and the focus keeps changing because they're coming toward you. Thanks for any input!