As far as I understand, such a situation has developed due to the format of the month-year dimension.
You need to show Qlik Sence the correct sort order. You can go in two ways.
1) on the sorting tab, select the "by expression" sorting and arrange the dimension, for example by date (see table 1 in the attached file).
2) More cumbersome, but also working way. When loading your data, show the sorting of the Month - Year field using the additional field (in the example shown, this field is ID). Then when constructing a diagram on the "Sorting" tab, you should also select the "By expression" option and specify the sorting by the special additional field (ID in this case - Table 2 in attached file).