Open a support case with a Discovery Diag and they can help. Give them 2 examples a device where it's work and one where it's not. Also, include Code version and Model( I like to use the same models if that is possible) https://support.infoblox.com
I thought I should close this out after Sif Baksh gave me the solution via a PM. For the particular case I was trying to solve, the answer is to use "$Device_deviceipdotted" instead of "$IPAddress". Thanks, Sif!