I typically just truncate (delete all of the rows) the `queue` table if something goes wrong with a task.

Then I delete all of the files in `storage/logs/` and I try to reproduce the problem. If it still happens, then I look in `queue.log` and `web.log` to see what the issue is.

Usually searching on `[error]` finds what I'm looking for pretty easily. Occasionally I have to browse through the file to find the actual problem, but that's why I delete the log files before I do it, so there isn't as much to wade through.

Relevant articles I wrote since this answer:

* [Robust queue job handling in Craft CMS](https://nystudio107.com/blog/robust-queue-job-handling-in-craft-cms)
* [Zen and the Art of Craft CMS Log File Reading](https://nystudio107.com/blog/zen-and-the-art-of-craft-cms-log-file-reading)