Extremely bright regions after warping individual FOD to population template

Hi MRtrix experts,

I was trying to register the individual FOD maps to the population template. I was checking the FOD maps after warping, and finding some extremely bright frontal regions in numerous of participants.

The T2 looks remarkable, so this is unlikely caused by lesion:

The original FOD and brain mask also looks perfect. I wonder if this is warping issue. The population template was built based on an unbiased sub-sample (n=40) out of 287 participants.

Thank you! Any advice is appreciated.