For whatever reason, these glitch/bug out. They do so when placed on a ground tile. Why this happens, I have no idea. However, one thing you can do to limit and hopefully prevent for good your equipment from glitching out is to place your tanning tubs or racks inside a building or onto a platform which will place the tub or rack above the ground. Those that have done this seem to have far fewer/no more problems with their tubs/racks. Why this helps, again, I have no idea - but it does help.