Aged fixed assets

Hi and sorry for prolonged topic in advance. First thing, I am not an accountant. Not even close.
My father owns a steel fabrication business and I’ve quit my job to take over. One of the problems of the business is a history of bad accounting system. That is why I am trying Manager.
We own a lot of machines purchased over the past 20 years (they worth a lot).
When I try to input the machines as fixed assets with old date, older than the start of Starting Balances date, it gets wiped off the system. When I input them with a false recent date, my cash in hand gets debited with the asset value amount (a negative number).
What is the best way to record such assets? I know the question might look silly, but …

When you are migrating to Manager from previous accounting system, you will need cost price of each asset and accumulated depreciation figure for each asset as at starting balance date.

Then you enter those figures under Starting Balances section under Settings tab.

See: https://guides.manager.io/15718 - the guide covers how to set starting balances for fixed assets too.

Even though the machines are worth a lot, from an accounting perspective they probably have a book value of zero by now as the original purchased cost would have been fully depreciated.

So when putting in their starting balances, enter a cost price (say 100) as well as an accumulated depreciation amount (-100).