Sometimes wallets/exchanges stop syncing:
  • shut down / get hacked
  • close to US users (e.g. Poloniex)
  • Coinbase vault that was deleted
  • etc.
In these cases, user funds are stuck on the wallet/exchange, and they remain frozen in time (non-zero) even after the funds are gone or after the users create manual edits. Potentially need to let users reset the current balance to the current cumulative value based on transaction history (instead of last synced current value).