I had a lot of trouble with this sentence:
Until I finally dumped the whole thing into jisho in frustration and found out that 取り返しのつかない is an adjective expression meaning “cannot be undone” and now it suddenly clicks. So posting that here in case others are confused.
Did the clock stop? The drawing looks like the second hand is still moving, but Kanami says 止まっちゃった like it broke again? Or is that line referring to even farther back when it was originally broken? And then she flashes back to おにいちゃん telling her to call him if it breaks again, but she knows she can’t so she’ll leave it as it is. Or is she leaving it as it is because it currently working is a reminder of おにいちゃん?