Timing keeps slipping

So I recently did a head gasket and am pretty new still to BMW. Now when reassembling the timing I used the tool but I had already had the intake manifold on so I didn't put the pin in the back. All I did was top dead center it and it started up but had a check engine like for camshaft, vvt, and engine performance, which all leads to the timing. So jump to today I have had the timing jump on me numerous time, today I went ahead and took the intake manifold off and put the pin in, timed it perfectly, replaced the VVT, eccentric shaft sensor, and the 2 Vanos Cameshaft solenoids. New spark plugs and coils. Reassembled everything and it wont even start now. Saying it's misfiring, won't even get up to an idle, so I'm assuming it jumped... again. Now I did torque the cam shaft sprockets to 20nm with the additional 180⁰ turns and it still jumps on me, what am I doing wrong here? I also have checked the valves each time with a mini camera, the camshaft goes out of time, but not enough to bend valves, just enough to annoy me greatly.