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Alpha Blending Mixer is blocking after layer 1 switching on

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I'm using Alpha Blending Mixer to put 800x600 overlay layer on RGB video stream(also 800x600). Overlay flow is Nios->Timing Adapter->DDR controller->Frame Reader->CPS(for splitting RGB and alpha). Then RGB goes directly to mixes din_1, and alpha goes through the timing adapter1, fifo, timing adapter 1 to alpha_din_1. My backgoutnd channel is BT-656 720x576 interlased video stream, which is transform to progressive RGB and goes to the Alpha Blending Mixer din_0 throuth the Frame Buffer. I'm using alpha_stub as alpha sourse for the Alpha Blending Mixer alpha_din_0. Mixer output connect directly to Clocked Video Output. Frame reader and frame buffer's MM master is connected to the DDR controller trough the pipeline bridge.So then I started my application, without din1 enabling I can see video on my screen, but then I switch on Alpha Blending Mixer din 1 channel I get freeze picture. As I can see on Signal Tap? all ready signals(except alpha din0) goes low after first packet of frame reader data , and also Mixer dout ready is low to, which is strange for me. Please find attached SignalTap exported pictures. It contain Alpha Blending Mixer both inputs and output. I would be very grateful for any help. I need to understood where the problem is.
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