Material usage variance (adverse)

The following are potential causes of material usage variance, select the ones which could properly explain an adverse usage variance and at the same time indicate poor performance of the production manager.

The business has separate manager for production, material purchase and machine maintenance .

1) Selection of new supplier offering similar quality for lower prices
2) Inadequate training of newly recruited staff in the production department.
3) Movements in the exchange rates causing more expensive materials
4) Machine breakdown due to delays in the annual maintenance schedule
5) Reduced quality materials bought
6) Change in the production process causing extra losses of materials

Sir correct answer are inadequate training of newly recruited staff in the production department and change in the production process causing extra losses of materials. But sir in my opinion, reduced quality material and machine breakdown due to delays in the annual maintenance schedule should also be the correct answer, but the suggested answer in kit does not include this, can you please explain me the reason?