Remember that in RPG MAKER MZ, F5 does not send you to the Title screen, it reloads the game.
And your project must be bugged, or you will have a compatibility problem. I have tested it in a clean project and installed the Visustella Core and I have had no problems. The character stats are maintained when the equipment has evolved.
I recommend that you try to test it in a new clean project to see if it continues to happen to you.