There's going to be a cleanup of the custom designs on May 6. You can view the list of designs to be removed on the discord.
You can also report additional designs on the discord too.
There are some custom designs that are misaligned
When you add new furniture in the right way, but use custom design, the furniture will be misaligned and reproduce the situation.
Ex.
New Oven by Luci
Eulmoran Bed by Sarabi
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Custom design Is there a ceiling on the number of furniture pieces or other problems that cause this?