Placing a PrimalCore barrel on grass with BetterFoliage enabled turns all grass surfaces the barrel is touching invisible. Disabling BetterFoliage immediately resolves the issue. Submitted an issue on BetterFoliage's github at https://github.com/octarine-noise/BetterFoliage/issues/163
Currently using A10's pack, which includes BetterFoliage 2.1.10, Minecraft 1.12.2, Forge 14.23.1.2575 and Java 1.8.0_151 64-bit.

this has been fixed
See An-Sar/PrimalCore/issues/125
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this has been fixed