You could've used the SDK instead: https://openwrt.org/docs/guide-developer/toolchain/using_the_sdk
Like my "patch", it's a dirty hack that violates the standard, but we had to employ them because most ISPs hire idiots with zero IPv6 knowledge, see my ISP's recent development: Odhcp6c issue with my ISP's configuration - #5 by Cthulhu88
Anyway, don't submit it as a PR (not that there is anyone there to merge it). Your badly configured ISP is sending a bunch of No Address Available status mixed together with success status, odhcp6c is behaving correctly.