If you think the image is damaged… that could of course be, it is pretty new. See the testing section at Server 2.5.1 WIP/Client 2.5.1 WIP to confirm. Then I’d need the exact, complete software involved to be able to (hopefully) reproduce the problem.
W.r.t. to grub stage 1.5, it should already be fixed, I just need to test+release a new version.