How to correct term alias? I don’t know why in Drupal 6 some of my parent taxonomy terms have duplicate URLs. For example, I have http://example.com/carrers-0 instead of http://example.com/carrers.
I am not finding any duplicate taxonomy term.

How can I correct it?
Once you had something under that alias, alias is treated as "used" and blocked from reuse.

Search http://example.com/admin/config/search/path (or similar page in 6, if address was changed) and look there for aliases you want. Remove them. Remove aliases with -0. Re-save your node / term / anything. That should do it.