Okay this is interesting. Usually WT doesn't like to air their squabbles, but maybe they are just doing it because the New York Times had a story on it (I can't read it because I'm not a subscriber)
https://www.nytimes.com/2022/01/25/arts/design/jehovahs-witnesses-nazis-lawsuit-museum.html
And here's the JW article:
https://www.jw.org/en/news/jw/region/germany/Jehovahs-Witnesses-Seek-Kusserow-Archive/
Anyway, it mentions that there was an ex-JW Kusserow family member who sold the memorobilia to the military museum, do we know who that is, or if they're apostate or just your average ex?