If you have an unignored worktree checked out in a subdirectory of the main working directory of a git repository, Dura will fail to capture any changes (whether by watch or capture).
Consider this example:
$ git init
$ echo 'beep' > boop
$ git add . && git commit -m 'initial commit'
$ dura capture # works correctly at this point
$ git worktree add -d wrktree HEAD
$ dura capture
Dura capture failed: invalid path: 'wrktree/'; class=Index (10)
If wrktree/ is added to .gitignore, Dura continues working fine.
This is admittedly a bit of an edge case, and perhaps an unconventional way to use worktrees, but Dura failing in this situation can also be a surprise to the user.