Stop working after few hours - #9 by xgreenx contains information how to upgrade the fuel-core.
As I mentioned in the previous comments, the off chain database(which is used to get users balances) is out of sync because of Handle incorrect shutdown of the off-chain GraphQL worker · Issue #1584 · FuelLabs/fuel-core · GitHub. You need to reset the database and sync again from scratch=( Unit issue is fixed