Another dead Husqvarna QC330 battery charger

[scbk]

It's 4yrs old but barely been used as it was a 2nd charger for when the main one was busy. Smell of burnt electronics.

 

The main charger is a QC500, 6yrs old, has been used a lot, and still works fine

 

Plenty of stories online of QC330 chargers dying. I wonder what is wrong in the design, they seem to have a very high failure rate.