Need For Speed Rivals [PC] + Logitech G29 some buttons doesnt works

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1) NFS Rivals officially don't support driving Wheels. Se this solution: Need for Speed Rivals Steering Wheel Support

2) Try to use the Logitech's official software  or third party key mapping software e.g. Xpadder & see if they will make that "problematic" buttons work.

p.s.: Sorry, I don't have personal experiences with G29 nor I know the exact solution to your problem.

Problematic buttons can be reprogrammed to the appropriate function , it will take some initiative , the tools you will be needing can be found in my post below

As you might not know, I created a post back in 2015 with explicit instructions about getting wheel support in NFS Rivals on the PC. It was approved by EA_francois , but someone decided to delete it. 

I put it back, see http://answers.ea.com/t5/Need-for-Speed-Rivals/Do-you-Want-wheel-support-in-NFS-Rivals-Click-here/m-p/5382832#U5382832 for my re-post.

The x360ce is what will allow the reprogramming of buttons,if you need help just post in my link, I am subscribed to it.