It rather depends on the environment in which you are working - if estimates are well estimates then there is probably little harm in guessing how long something might take to fix. However, some places treat "estimates" as binding commitments and then it could be risky to make any kind of guess because someone will hold you to it.

More than some places. Every place I've worked, has been a place where you estimate at your own peril. Even when the manager says "Don't worry. I won't hold you to it. Just give me a ballpark.", you are screwed.

I used to work for a Japanese company. When we'd have review meetings, each manager would have a small notebook on the table, in front of them.

Whenever a date was mentioned, they'd quickly write something down.

Those dates were never forgotten.