If you don’t know the root cause of the bug, you can’t estimate a time to fix in any meaningful way. Don’t even try. Misleading data is far, far worse than no data.
That said, bugs absolutely should be prioretized. Ask yourself:
- Is this bug blocking critical customer workflows? (Primary purpose of the app, signup or payment flows?)
- How many users does the bug impact? Is it affecting 100% of the users, 1%, or just one person?
- Does it happen every time, or is the problem intermittent?
- How many times has the bug been reported? Is it blocking customer support from dealing with other issues?
Ideally your quality engineers have collected most of this data and included it in the bug report before you ever see it in your issue tracker.
All software engineering time estimates are worthless lies. Once you’ve done enough work on a bug to figure out how long it will take to fix, you’ve already diagnosed a root cause, and that’s 90% of the bug fixing work.
The rest is just making the change and seeing it through the deploy process.