trouble while using two video source with DE2-70 board

In addition to this, i am trying to use SignalTap II logic analyzer tool. to observe the signals.

In signalTap II logic analyzer settings, when i set iTD1_CLK27 as clock, the video from the first video source is working perfectly, but the second one is not.

When i set iTD2_CLK27 as clock for SignalTap II settings, this time the video from coming from the second video source is working perfectly, but the first one is not.

I thought that, there is a timing problem in my design. Because There is no change in my code, by only changing Signal Tap II settings, the expected result can be changed. i just want to see both of video coming from the two source by switching between them.

Any idea will be very usefull for me. THanks...