Put the summary of the bug you're having here

What I expected to happen was that when I use the latest snapshot to open an old map of Version 1.8.9, every item frame and the map it hold should remain unchanged.

What actually happened was that SOME of the item frame become invisible but there are still occupying the space while the others remain unchanged.

I don't sure if it was just my map problem or the new version Minecraft have bugs.

Steps to Reproduce:(May not work)
1. Put maps on different item frames in Version 1.8.X
2. Use Snapshot to open the map
3. Some maps on item frame may disappear

The attachment include screen-shots of the same map in version 15w51b and 1.8.9