You can also turn on persistence debugging with log:set DEBUG org.openhab.persistence.mapdb to make sure its writing correctly to mapdb.
/opt/openhab/conf/persistence/mapdb.persist
Strategies {
default = everyUpdate
}
Items {
// persist all items on every change and restore them from the db at startup
* : strategy = everyChange, restoreOnStartup
}
default=mapdb