happy to report you can skip building the vulkan shaders even after a game patch, so i guess just build the vulkan shaders if the message comes back, probably with a map change?
I've spent well over an hour building the vulkan shaders it got stuck on 99%(i think so anyway) but after skipping it, the game started pre-loading the map and shaders and the message cleared.
Will see if the new patch requires the rebuilding of vulkan shaders again.
