UPDATE: Turns out there was a problem with my NVIDIA driver settings, and I'm actually a big dumb! I don't know how to delete this, so if someone could mark this as "resolved" that would be great! Huge thank you to user Michał Gajewski for pointing this out!
This bug came up in one of the 1.15 pre-releases, but still exists in 1.15 and the pre-release for 1.15.1. I created a new world, and noticed that there was a weird pattern of lines appearing on all of the blocks. I don't know what is causing this, and changing the graphics does not fix the problem.
Environment
Windows 10 version 1909 (64-bit); Java 64-bit build 1.8.0_231-b11; AMD Ryzen 7 1700 8-core processor, 16GB RAM, NVIDIA GTX 1060.
I had the same issue, please watch this:
https://www.youtube.com/watch?v=pYRJzYhnEGw&list=LLGrQpk88RKrfwvSZauzVccA&index=35&t