I don't know how to explain this issue,
when i've got a wrong block in my loaded schematic,it's impossible to place a block on this block, like the box of the red wrong block disallow me to place a block,
in the same way i can't place a block through a ghost schematic block down face.
For example, if i try to place a block on a grass_block through a schematic block, it does nothing.

Sorry for my english, i'm french so i don't know how to explain in goods terms this issue

There are two possible causes for this:

• You have the Pick Block Last keybind set, and Pick Block enabled, so it will change the item in hand when you try to place a block through schematic blocks
• You have the Placement Restriction mode enabled, which tries to prevent wrongly placed blocks

Have you ran the verifier/are you looking at the verifier's "thicker overlay"? There is currently a bug that messes up the ray trace result for the Easy Place mode and possibly also the Restriction Mode if you look at a verifier hilight overlay. Basically preventing placing a block in the Easy Place mode if you are looking at a verifier hilight box.

If this is not the issue, can you record a short video clip of it or at least post a screenshot or something to better explain what is happening?