The Graph only shows items that contribute to your profit.
An incorrect bank balance happens because the data hasn’t been reconciled to the bank correctly. It is up to you to check that the opening balance is correct and that the bank balance is correct after each bank statement import (or after entering any transactions manually).
You could have your GST Return type set to “Invoice Basis”. This means that it will use the date of the Invoice rather than the date in the cashbook. We recommend that where possible companies use “Payments Basis” because it is a lot easier to use