When integrated circuits ("chips") fail explosively, blowing a hole in the top of the plastic encapsulation, it's usually due to excessive current and very rapid overheating. Clearly, in this design, the fuse protecting the circuit is either too high in rating or the fault current is taking a path not protected by the fuse. Either way, the design is clearly lacking but I guess the designers can't anticipate every possible failure mode.
If anyone has one of these units (that still works) open, a good close-up photo of the board would be good to help us identify the "chips" so that replacement/repair can be attempted. Once the "chip" has a hole in it, the label is gone...
