I posted a while ago about the same problem here. It seems to happen on numerous skins. I think it’s an OSMC issue though as I have exactly the same setup on a Pi, Windows 10 and an Android tablet and it only happens on Pi. Have tried several fresh installs and is only when the login screen is enabled. It’s fixable by changing font in Skin Settings. It shows as blank. Change it to anything and then if you want change it back to default.