I managed to reproduce this very rare verification error in CROSS-RDSDPG-128-small. I'm still looking for the root cause but I can confirm that it seems totally unrelated to the new fuzzing harness.
It looks like there is a problem with the size of the array used store paths in the seed tree while signing. I'll open a new PR as soon as I find a solution, it should be a minor fix.
Originally posted by @rtjk in https://github.com/open-quantum-safe/liboqs/issues/1955#issuecomment-2432126812