For example, let's look at the IV.

Symmetric encryption algorithms usually need an input called the initialization vector (IV), but different algorithms have different requirements.

AES-CBC requires unpredictability, but AES-CTR (and AES-GCM) require uniqueness. Misunderstanding of these requirements have led to real world attacks, see for example BEAST or https://eprint.iacr.org/2016/475.pdf.