LMX2594: Observing strange locking behavior on EVM

Hi Team,

My customer is using the LMX2594EVM and the board they have appears to be demonstrating some aberrant locking behavior. There are two screenshots below comparing excessive sideband/reference leakage at 12.1GHz and normal behavior at 12.3GHz.

Is this expected? If not, do you have any ideas on why it might be behaving in this manner?

The sideband level increases with increasing charge pump current. The photos shown are at 3mA charge pump current. Could this potentially be a faulty EVM?

Here are the photos:

(Bad)

(Good)

Thanks!
Mitchell