If the error doesn't stop after disconnecting from power (didn't in my case) there is a technical defect.
Uhm, yes, I supposed so.
Furthermore: it is not possible to offer service or support for this device after its period of guarantee cost-efficiently.
Buying a new device would be the more economic solution.
Sustainability? Cost of disposing of the old device?
The reply from #Eaton describes a broken reality:
"We cannot offer a repair. There are no spare parts or products in this price range nowadays. Most times one hour of work already is more expensive than a new device.
In this aspect products from other companies are not different from ours."
Sad. No #Repairability.
I'll ask them about an option to rescue the old ups from dumping and repairing it.
Furthermore I'm really interested in their opinion why I should decide - given my experience with their product and support - to buy a product from their company again.