You should reset your config.yml if you want avoid problems and especially if you want to migrate to MYSQL.
I recommend to make a backup of Sanctions.yml.

Fix update checker saying the plugin isn't up to date (still a little bit slow because of spigot api).

In game you can use /rsadmin migratedb
This will help you to understand how it works.

Also my method of storage has changed, your sanctions.yml will be rewrited.

History of sanctions will come very soon but will have some issues due to the lack of information of my old storage method was storing.