We're not able to recreate this problem on our end. There is no need for you to encode your input. Xeams does that in the background.

 

I have created a small video demonstrating that you should be able to add a body filter and search that in incoming emails. Please download the video from https://shares.synametrics.com/app?operation=pubopp&id=1610984543071X47A23A87A62MtZ9w