Under a set of conditions I don't fully understand, the rail blueprint tileEntity renders almost fully transparent/invisible. This seems to be related to travelling near the world origin. But the effect seems to almost toggle on and off, so once it's active it will remain active in a large (sever hundred blocks) area, then once it deactivates, you have to get much closer before it turns back on. It's highly sensitive to player facing, and while the bug is active it can affect anywhere from 1 specific track direction to all of them at a given point. I wasn't able to suss out any pattern on what directions make it invisible, or what locations correspond to what severity of the effect. I always had to travel below about y=30 to activate the effect though, so this shouldn't affect the average player. Bugged blueprints can still be built and interacted with normally.

bugged blueprint:
https://cdn.discordapp.com/attachments/404147177775038487/551668514591866890/unknown.png

what it looks like before placing:
https://cdn.discordapp.com/attachments/404147177775038487/551668576545669120/unknown.png

normal blueprint (note only a slight facing change):
https://cdn.discordapp.com/attachments/404147177775038487/551668554668179466/unknown.png

IR version:
Master branch as of Feb 28, also present on 1.5.0

I've noticed this before but I forgot to mention it. I only observed it while I had a rail fill selected. From what i can tell, this was occurring irrespective of y level for me.