One thing I remembered with the HR40b … there are a few different versions of the fat-40 universal board ….. some do not take kindly to EPROMs as character roms … they can offset the character count on the screen so the previous line ends with R of ready for example.
I know the boards that have the metal shield box over the piezo work just fine. If the board is a univ 1 version it could have the issue with EPROMs as character roms… pretty obvious when you boot up.
If you have lots of vertical lines then make sure the board is pushed in all the way around the character rom and the piggy back socket is correctly mounted over the crtc chip … also the cable isn’t shorting on other pins in that socket.
Andy