The blocks of the schematic do not show up as real blocks. I have tried using 1.8.9 1.12.2 and .1.14.4 and they all appear the same. Any help?
(edit) Please comment if you too have the same issue.

After a bit of a hiatus (mostly something like a mod updating and breaking Minecraft yet again...) I logged in and changed some settings cause my FX6300 and GTX750Ti were only giving me 10 FPS, I had this issue, Thanks for the fix, Fast Render is still on but the Render Regions is now off and fixed everything... If you have Fast on it disables Shaders so no need to turn them off... the Regions thing was also causing my game to lag and eventually freeze and so this fixed that as well...

Definitely having the same issue, was hoping someone else would have commented with a fix.

UPDATE: Found the fix when looking to get Litematica instead.

"Render Regions needs to be disabled
Shaders need to be set to OFF, or alternatively disable VBOs in the vanilla Video settings, and disable both the 'schematicOverlayModelOutline' and 'schematicOverlayModelSides' options in the Visuals category
Fast Render might also need to be disabled if there are still some weird HUD/GUI rendering issues"

Setting my shaders from Internal to off and turning off VBOs fixed it for me. Hope this helps someone else.

Definitely having the same issue, was hoping someone else would have commented with a fix.

UPDATE: Found the fix when looking to get Litematica instead.

"Render Regions needs to be disabled
Shaders need to be set to OFF, or alternatively disable VBOs in the vanilla Video settings, and disable both the 'schematicOverlayModelOutline' and 'schematicOverlayModelSides' options in the Visuals category
Fast Render might also need to be disabled if there are still some weird HUD/GUI rendering issues"

Setting my shaders from Internal to off and turning off VBOs fixed it for me. Hope this helps someone else.

Thank you for this.