They just become invisible after few minutes or randomly. I don't know what it cause, the structure is still there. The render region is off.
latest.log

Builder's+Tools+-+1.2.0
CreativeCore_v1.10.28_mc1.12.2
LittleTiles_v1.5.0-pre199_64_mc1.12.2
Optifine_1.12.2_HD_U_F5

This is a duplicate of #506 can you please post your config file there? I actually need all the configs (also the vanilla and optifine ones).