Hi, I have a problem with liveview focussing on my Nikon D750 and Tamron SP 24-70mm f/2.8 DI VC USD Lens. The camera/lens will focus correctly until the first time it can’t focus (e.g. object too close, not enough light). From that point the camera refuses to even try to focus on anything in liveview mode. Switching the camera off and on again doesn’t help. The only thing that works is switching the camera off, detaching and reattaching the lens and switching it back on again. The issue is repeatable 100% of the time, every time the camera and lens first lose focus in liveview mode. Can anyone suggest the cause of the problem and a permanent fix? I’ve previously owned the same equipment and had no such problems. I don't currently own another lens so can't confirm if the problem is with the camera or the lens.