What happened? - Attempting to paint background walls results in many tiles that cannot be painted. What were you doing in the game at the time? - Painting background walls. Whether you were able to trigger the bug again by repeating what you did. - Yes. It occurs 100% of the time but I don't know a way to tell which tiles will experience this. Your operating system name and version. - Windows 10 x64 (1703) Are you using any mods? - no Whether you're in full screen or windowed mode. - tried both fullscreen and windowed. First noticed the bug in windowed mode It appears this bug has been in the game since 1.0 at least. There is a workaround where you can place foreground blocks over the background tiles that refused to be painted then paint the foreground the desired color then break the foreground blocks and the background remains the desired color. At this point I am not sure the devs even know about it as it breaks basic functionality of the matter manipulator and it has been in the game since release. Maybe it isn't a bug and is intended? Would be nice to know what the status is on this issue.