A similar but not identical problem afflicted Voyager 2 in 2010. Received science data (but not engg data?) was garbled.
The problem was traced to a flipped bit in the program stored in the FDS. A command was sent to flip the bit.
The issue was diagnosed by downloading a full memory image, which implies that engg data download was working.
This is probably what was done today with Voyager 1 today. Hopefully, it is a similar problem.
https://voyager.jpl.nasa.gov/news/details.php?article_id=16
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