Is the banding happening while previewing the video or after rendering the file? If you are importing the same media from After Effects, please navigate to Project Settings > Color > Depth and change it from 8 bits per channel to 16 bits per channel. Render and export the video to Premiere.
In Premiere, in your export settings choose a codec that supports high bit depth (such as Prores 422) and make sure that Render at Maximum Depth is selected. Also, select the drop-down box next to Depth and select 16-bpc.