Hi again,
Thanks for your advice. I believe I’ve found the issue and corrected it using MySQL Workbench. It turns out that the ID column in the the WP-Redirects table in the database was not set to “auto-increment.” So every time that a new redirect would be put in, it would give it the ID number of 0. And thus, not allow any more ID increments.
But just changing that setting on the DB table seems to have fixed the issue.
Thanks again!