Want a particularly egregious example? Here: https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=celex:62...

Police in many EU countries was systematically searching suspects phones without mandatory due process. This was prima facie illegal, everyone involved knew it. They did it regardless.

Yeah, this decision eventually resulted in many governments issuing new guidance, and some countries rewriting their national legislation. Is that a big victory for the rule of law? I think not, the national governments should not be knowingly violating the ECHR in the first place.