AD9833 output issue--jitter

Hello,

   We design a square wave generator using AD9833, The output frequency is below 40K.  We find some frequency point is stable, some is instability. Below video is instability , it sway from side to side.  How i improve this ? Thanks



AD9833
[edited by: Aggil at 1:40 AM (GMT -5) on 20 Jan 2021]