A suggestion to add a field to the Source information called Index Notes as a place for us to note if there are indexing errors on a record when editing of the record isn't possible, for whatever reason. [Or give instructional text on how we might tag notes of this type with something like #IndexFix]
Instructions for the field could ask for notes/sources/reasoning for something being listed there or restrict access to the field to folks with an appropriate access level (folks that have worked on indexing efforts, gone through training, etc).
Having a field for that (or a tag you can search for) would allow you to pull out those notes in a report for volunteers to help with editing the index if that capability was added in the future, or to send a report to the provider of the data.
For now, I'm putting this type of note in the NOTES field for the Source.
Many thanks for this great resource!