My 108V Cordless Lawnmower is having issues with the height adjustment

The cutting height is centrally adjusted by the cutting height adjustment handle. Different cutting heights can be selected as follows: 

You would need to check the connections between the height adjustment lever, rear axle and the connecting rod:

1. Pull the cutting height adjustment lever outwards. 
2. Move it forwards or backwards to select the desired cutting height. 
3. Return adjusting handle back into place. Make sure the lever is secured in position. From position 1 to position 7, the cutting height ranges from 25mm to 75 mm.