IIRC something about the pain used on the aerodynamic outer shell (the gas cells inside were separate gas tight balloons made from processed cattle stomach tissue (!)). This paint apparently turned out to be highly flammable and/or explosive and could be activated by dischrges of static electricity.

I think there was static discharge involved, and thermite paint. And of course a giant bag filled with hydrogen, surrounded by oxygen.

Iirc there is a great YouTube video with Bill Hammack about this. Highly recommended. https://youtu.be/ixxXhZVFXxQ

He also wrote a book.

Rips along the seams of the fabric siding causing large surface areas of hydrogen to be mixed, I think?