When you are working with a Koha database, installed many years ago and upgraded since then, you may have quite a bit of small deviations from a freshly installed database.
This may be due to small inconsistencies between the changes to kohastructure and the atomic update files, among other reasons (failing dbrevs, local changes, etc)
Some changes only involve for instance the order of the database columns but others may be a bit more serious: NULL or NOT NULL, type of constraint (RESTRICT or CASCADE), etc.
You can have an idea of the state of your database by running the dbix script in the misc folder [in a safe way :) ] and looking at git diff.
This report only collects links to individual reports where such changes are reported / resolved.
Note that I counted changes in about 45 tables (read: DBIx schema files) recently before starting to resolve them.