I've been noticing this when playing through the game in both 1.14 and 1.15 versions and its become a mild annoyance. The mipmapping is doing something odd on the sides of blocks. This is what it looks like:

This image is zoomed in.

I'm not entirely sure if this is the game itself or just my GPU but I've never had mipmapping do something like this on my computer before so you can see where the concern is coming from.

This problem shows up in every world and never ceases even if I restart the game. Note that it only shows up on horizontal facing blocks (North, East, South, and West). I haven't honestly tried very many things to prevent this from happening because it doesn't seem to be a major problem but I thought that in the event that it is a bug, and not my GPU, I would point it out.

Anyway, cheers and good luck figuring this out.