Pioneer BDR-208DBK inconsistent rip

I recently picked up this drive and have had great results until I tried to rip Avatar. 2x for most of the rip but it apparently hit 4.7x at some point.
Average Read Rate: 8,781 KB/s (2.0x) - Maximum Read Rate: 21,326 KB/s (4.7x)
I’m not sure how it’s read speed is limited for some discs but not others. Are there any options for removing this limitation?