Encoding video with x264 for Sony DoStudio Blu-ray authoring. Occasionally I get something similar to this error.

Main video average bitrate of last 30 frames is 47289715 bps.
Main video average bitrate is higher than MB leak rate (40000000 bps)
Please check main frames around GOP #2
My x264 encode settings:

-b:v 35000k -maxrate 40000k -bufsize 30000

What would be the best way to fix this error?