Failed to load skins when offline

This bug always happens to my skins when I'm offline it always says "Failed to load character #"

I can't edit the skin slots with skins that had "failed" to load

 

When you're using the skin that you edited from skin editor, you'll return back to default Steve/Alex skin

Custom skins and Unedited steve/alex skin were fine, but sometimes it will "failed" to load too

 

But when I'm online again, the skins are back but the downside is that I don't always play online