Mazda 6 Service Manual: No.9 abnormal shifting

No.8 does not shift to fourth gear (4gr)

No.10 frequent shifting

Other materials:

Mazda 6 Service Manual: Manual Transaxle Shift Pattern
  The shift pattern of the transaxle is conventional, as shown. Depress the clutch pedal all the way down while shifting; then release it slowly. Your vehicle is equipped with a device to prevent shifting to R (reverse) by mistake. Push the shift lever downward and shift to R.   ...

Mazda 6 Service Manual: STEP 3: Contact Better Business Bureau (BBB)
Mazda North American Operations realizes that mutual agreement on some issues may not be possible. As a final step to ensure that your concerns are being fairly considered, Mazda North American Operations has agreed to participate in a dispute settlement program administered by the Better Busi ...