Custom attribute are can’t deleted.

I am using Events Manager in a Japanese environment.

After I created an attribute (such as #_ATT {***}),
I removed it from the general settings because I didn’t need it anymore,
but it’s still there when I create a new event.

I thought it was because I created the attribute with double-byte characters,
but it was the same with single-byte characters.
It doesn’t seem to be a plugin conflict.

I looked into the database with reference to similar reports in past forums,
but couldn’t find anything like that.

I would be happy if you could let me know if you have any ideas for the cause.
Thank you for the wonderful plugin.