When measuring voltage from a converter, always measure between the legs.

How those voltages relate to earth, depends on the kind of step-up transformer they've used, and if they've connected to the mains input or earth at any point.


If it's now working again, all you can really do is wait until it stops working again.
Personally, I'd be wanting to ensure the supply voltages are 100% before looking elsewhere, which is why I keep asking about voltages.