how to reproduce:

1.enable block crack fix in falsetweaks settings
2.build a wall out of something (I made it out of earth)
3. The edges of the blocks will start to flicker

mod list:

00gasstation-mc1.7.10-0.5.1.jar
falsepatternlib-mc1.7.10-0.10.14.jar
falsetweaks-mc1.7.10-2.0.2-hotfix1.jar

That's by design, decrease the BLOCK_CRACK_FIX_EPSILON value in the config. The default value is 0.0005.