This reminds me of a (possibly unrelated) incident involving a C-130A that broke up in flight while serving as a fire-fighter water-bomber. It turns out the original material 7075-T6 wore too quickly and should've been the revised material 7075-T7531. Even C-130B's through C-130E's weren't fully-upgraded with the recommended engineering changes.

http://www.iasa.com.au/folders/Publications/Legal_Issues/Pea...

https://en.wikisource.org/wiki/NTSB_accident_summary_for_N13...

https://aviation-safety.net/database/record.php?id=20020617-...

Here's a structural analysis of the C-130H wing design:

https://fenix.tecnico.ulisboa.pt/downloadFile/395138005046/C...