The probe has been sending gibberish science data back to Earth, and scientists feared it was just the probe finally dying. You know, after working for 50 GODDAMN YEARS and LEAVING THE GODDAMN SOLAR SYSTEM and STILL CHURNING OUT GODDAMN DATA.

So they analyzed the gibberish and realized that in it was a total readout of EVERYTHING ON THE PROBE. Data, the programming, hardware specs and status, everything. They realized that one of the chips was malfunctioning.

So what do you do when your probe is 22 Billion km away and needs a fix? Why, you just REPROGRAM THAT ENTIRE GODDAMN THING. Told it to avoid the bad chip, store the data elsewhere.

Sent the new code on April 18th. Got a response on April 20th - yeah, it's so far away that it took that long just to transmit.

And the probe is working again.