The bug
While making some changes to my map I noticed all the roofs on my building disappear on the map as well as brick paths becoming invisible allowing you to see blocks underneath them in the map instead.
Known affected blocks:
Brick Blocks
Brick stairs
Polished Granite
Polished Andesite
Spruce Planks
Oak Slabs
Stone bricks
stone brick slabs
stone brick stairs
crops
Linked issues
is duplicated by
Attachments
Comments


Hello I ran some additional tests and here is my results. The World was created in 1.12, I have opened it in almost every snapshot and pre-release. I missed some of the earlier snapshots but I don't remember which.
Here are the results of some tests I did.
In the current save file I tried making a brand new map. Making a new map does not make blocks reappear. Taking the same invisible blocks and piling them on top of visible blocks makes them visible on map. Replacing blocks with the same block does not fix the issue.
I then used a saved back up of Pre-Release 4, map functioned normally. I then took this back up copy and updated it into Pre-Release 5 where the map once again broke, making certain blocks invisible again.
Re-created the world seed in Pre-release 5, and the map is still broken with certain blocks being invisible unless you stack the same blocks on top of each other.

I've added some additional photos to the original post.
Confirmed. This seems to happen in some circumstances when there's air below the block the map should render (and some other obscure cases), no matter what kind of block this is.

I built a bridge out of spruce wood blocks and they won't show up on Pre-5, but they did on pre-4. Also, Dark Oak slabs don't seem to show up. I made a map of a Woodland Mansion and you can't see the roof, just the interior rooms.

Could this bug be related to the renaming of internal IDs made in pre5?
Probably not. All kinds of blocks are affected.
In what version did you create the world, what snapshots did open the world?
Is the issue persisting when you recreate the world in 1.13-pre5?