This is a feature request, not a bug.
Files on network shares are not indexed by default. I use 'balooctl index' in a script to index files in those locations. They can be found nicely with baloosearch or in the various GUI tools. When such a file is modified, the updates are not indexed automatically, that's expected. But these updated files  cannot be indexed again manually. 'balooctl index' says they are already indexed. It's not sustainable to periodically delete baloo's database and recreate it again.

I wish balooctl gets a 'reindex' option, which would clear old entries related to a file and dig through it again. Ideally, it should do anything such only if the file has been modified since the last time it was processed.
Or balooctl could get a 'clear' option, which would remove any entry for a file. A nightly script could search for files modified in the last day and call 'balooctl clear' and 'balooctl index'.

For now, baloo writes in stone network files processed manually .

Thank you for considering.

Reproducible: Always

Steps to Reproduce:
1.Call 'balooctl index' for a file on a network share.
2.
3.

Actual Results:  
Skipping: <file>

Expected Results:  
Reindexing <file>

baloo version : 5.13.0
KDE Frameworks 5.13.0
Qt 5.5.0 (built against 5.5.0)
The xcb windowing system