Main Accounts linked to the Asset Leasing Module should be able to be locked through the "Do not allow manual entry" feature (General ledger > Chart of accounts > Accounts > Main accounts > General > ADMINISTRATION).
These are control accounts and should be locked from manual entry to prevent accidental postings from outside the Asset Leasing module.
In the current design, with the mentioned feature enabled, the system throws a warning when posting several types of transactions, including depreciation. This warning makes the system post the voucher transactions to the “999999” Error Account instead of to the account set in Asset Leasing Parameters. The manual workaround of disabling "Do not allow manual entry" and using Posting validation to specific users is not feasible in some scenarios.
For all other modules, including fixed assets which is closely related to the asset lease module, if a control account is in use, then the posting is made to a locked account via a system/module posting. Thus, if this is a control account to which the sub-ledger should reconcile, the approach is showing an inconsistent behavior, not following standard accounting needs/processes.