There is a button all the way at the bottom of that list that refreshes all the workshop maps currently subscribed. This will likely fix the problem.

It happened to me also with Pacman Ultra Boss, seems Steam cloud size limitation concerns not only upload, but also download. Actually, that map has a file size over 500KB, that's more than half of the Steam cloud storage for Unepic.
I posted a solution at this post.

Map didn't last much time, and I was too busy dodging boss projectiles to be aware of any skin changes. Maybe the author should remove each non used skin (replacing it with a one color/transparent image for example) or lower the number of skins used to lower file size, as currently anyone who is suscribed to a few workshop maps won't be able to download it. Also check custom backgrounds, as that might increase file size too.

I don't know forsure if it is the skins that are causing it, unless it is the specific action of switching through skins that is causing it. My 60+ room map has 4 skins on the boss, 3 unused for editting purposes, yet the entire map takes up 1/10 of his.