It would appear that there are two IP addresses trying to be inserted, which exceeds the length of the cell in the database; we really need you to fill out complete error logs, along with your URL, any modifications you've installed, and how we can replicate the error...
Note that
NO modifications to the base software are supported, and this includes modifying your database and mysqli.inc.php file to run utf8mb4, as the software just doesn't support it at this time.
Any "data too long" errors are directly related to your attempt to insert a multibyte (utf8mb4) string where a single byte (utf8) is expected (as it takes up more space that what is anticipated).
Please stop posting issues directly related to your unsupported usage of utf8mb4; we're not just going to magically be able to make it work with the wave of a wand, it'd take a significant amount of time which we're already using for further PHP7.2+ updates.
You might even need to
File a Support Ticket with the vendor (we're here simply volunteering our time) so that your hosting environment and forum files can be checked.