Understanding Society User Support

This question is on the variable a_lmend (how marriage/ civil partnership ended) in the first wave of Understanding Societies: the third category (97 ‘something else’) of the variable a_lmend consists of a fairly large amount of respondents (1.237 / 9%) and I was wondering why such a large amount of respondents belong to this category. So, when do respondents get a value of ‘97’ on the a_lmend variable?

Many thanks.