paginated report Mutiple value parameters not working as expected

We are using power bi dataset to create and paginated report with mutiple cascade parmeters, with cat, sub cat1, sub cat 3, sub cat 4, sub cat 5.

We select mutiple parent categories, cooresponsing sub cat1 should fill, our dax works fine for single secltion, but fail when we do select all, does not return epected results when we select more then 1 category from parent.

Code we have written.

EVALUATE
SUMMARIZECOLUMNS (
'dim Pcat'[subcat],
FILTER (
'dim pcat',
'dim Pcat'[subcat] <> BLANK() &&
(
ISBLANK(@cat) || -- Handle empty parameter case
CONTAINSSTRING("," & Cat & ",", "," & 'dim Pcat'[cat] & ",")
)
)
)