Steps to reproduce:
1. Load up a new 1.12.1 world (preferably in Creative mode for flying around)
2. Find a high Extreme Hills+ biome (Cold Taiga also should be the same; I recommend seed
: -1617937944, and /tp 25 105 8)
3. Observe that snow on a few of the trees is cut off in straight lines.
4. Notice that this bug seems to occur only along subchunk boundaries