Hi Clogger
Q1 - When you set account opening balances under Setup > Balances > Account Opening Balances, the opening balances must have a net of $0, in others words the debits must equal the credits - if not the outstanding balance gets posted to Historical Balancing - this is to ensure the Balance Sheet balances. This is how it is meant to work. However with AR202x, there are a number of known bugs with Historical Balances, with errors causes by changing some accounts from Details to Header and vice versa. MYOB gets 'confused' and adds random amounts to the Historical Balance total.
Q2 - These are further bugs in AR2023 caused when accounts are moved up and down or renumbered, or changed from detail to header etc.
You may need to get MYOB to run a script if your file is online, if offline you may need to send the file to MYOB to get repaired, or to someone else who repairs .myox files.
Regards
Gavin