IS SA weak batting second?

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In the last 4 years, they have lost few tests batting second. Only two while batting first. 84------ 25.1------ 3.33------ A2 124----- 40--------- 3.1-------- A1 331----- 133.2------ 2.48------ B3 133----- 50--------- 2.66------ B3 138----- 57.3------ 2.4--------- A2 195----- 62.1------ 3.13------ A2 220----- 81.1------ 2.71------ A2 260----- 74.5------ 3.47------ B4 278----- 86.5------ 3.2--------- B4 291----- 119.2------ 2.43------ B4 343----- 108.3------ 3.16------ A1 370----- 132.2------ 2.79------ B4 Does anyone know why are they not so good while batting second??? It is not that their 4th innings but the 2nd innings of the game that they are weak in.