Some MCD files MapView seems to pretend don't exist, and it seems to be no error in the MCD file. I've checked them head to toe over and over again and I can find no reason MapView could possibly dislike the files, I've even scrapped them and rebuilt them from MCDs it does like, and still it seems to dislike the file. The name is fine, the items in the file is fine, but somehow everything together isn't fine and MapView won't give any reason as to why it dislikes the MCD. It'll load maps made for the MCD just fine on any wrong MCD, but when you set a map to load one of these MCDs, MapView acts like the MCD doesn't exist in the folder.
I had this happen first when I changed the Skyranger top east fin to be a wall instead of content. A very simple change to a MCD that MapView accepted caused MapView to ignore the MCD. Deleting it and re-making from scratch saw the same issue. I tried different names, using naming conventions that work with other MCDs, but it still ignored it.
Now I'm having the same problem with the DRAGONFLY MCD from XComFiles. I can't see anything wrong with it, and it loads fine both in MCDEdit and openxcom, but MapView seems to think the file doesn't exist. I've successfully loaded multiple other MCDs and maps from XComFiles and had no problems. I am 100% certain I did not make any spelling errors.
Here's the MCDs that aren't working with MapView. DRAGONFLY_DARK also doesn't work in openxcom though it loads fine in MCDEdit.