AD9910 Synchronization - Random Phase shift while iterating of I/O update or Change of Frequencies

Hello,

I am trying to perform AD9910 synchronization using two evaluation boards. I am using ADCLK846 as a buffer to send LVDS signals of SYNC_OUT.

I was able to synchronize both the boards but randomly I see a phase shift if I iterate the IO update or change the frequencies. 

In my application I am trying to change frequencies from 50 to 350 keeping the signals in phase. It would be great if anyone could help me resolve the issue of random phase jumps.

I attached a video of what's happening. The signals you are seeing are the outputs of AD9910 and few seconds into the video the phase randomly changes. In the video,Signal 2 is on top of Signal 1 



Grammatical mistake
[edited by: sundarsingh at 8:34 PM (GMT 0) on 2 Jul 2019]