Yesterday, I had a Grammar exam and I came across this question, I tried to look everywhere on the internet but I couldn't find anything related since "used to" always comes as a habit and followed with a contrast.
The sentence is "He used never to drink so much coffee, before he went to bed." According to the question, it must have two mistakes, so my answer was: "He used to drink so much coffee, before he goes to bed."
The exam now is nothing I'm worried about, I just want to benefit so I don't make a mistake again.