I chose to stick with the older kernel for now since I can't think of a way to debug the kernel version issue (no way to look into the machine since ESXi loses all network connectivity)
Could this be somewhat related?
Edit: I updated to 24.7.10 with kernel 24.7-n267981-8375762712f and things boot up fine. However clients are still unable to use v6 but the router itself is able to.