Let’s not forget that Gewirtz is incredibly close to Rock. I won’t call him a ‘yes man’, but he’s got that level of access. This whole thing where he’s deflecting from the Rock and blaming Cody is just the kind of spin that would come from Rock’s camp. Whether he liked it or not, Rock handled it incredibly well. This is just dirt sheet bullcrap.
I’m a little lost on how a container would mess with your boot loader (GRUB). That aside, most of what you’re explaining to do with the containers. These are OS-agnostic. What do the container logs tell you?