Review the sentence:
Struggling with the tight jeans, the zipper would not budge.
Struggling with the tight jeans, a participle phrase, has no target in the sentence. When a modifier has no word to describe, it is dangling.
To fix the problem, you could revise the sentence like this: Struggling with the tight jeans, Chris could not budge the zipper. Adding Chris to the sentence lets the reader know who should pick something different to wear!