I had never heard of this and took a look at the Wikipedia page you linked.
> Contact with STEREO-B was lost in 2014 after entering an uncontrolled spin preventing its solar panels from generating enough power, but STEREO-A is still operational.
> Contact with STEREO-B was lost in 2014 after entering an uncontrolled spin preventing its solar panels from generating enough power, but STEREO-A is still operational.