Co-pilot flexible sight problem

After a while I'm back to the UH-1, now I got into a problem. I can't use Opentrack with mouse to control Flexible Sight (co-pilot's sight). Before I can view and control Minigun with mouse at the same time. Now I have to disable Opentrack to use the Minigun.

I posted a demo video on DCS facebook group, please take a look.

https://www.facebook.com/groups/DigitalCombatSimulator/permalink/1103992346393448/?comment_id=1104307579695258&notif_t=video_processed&notif_id=1484180290766985

Thank you.:)