This mod has an incompatibility with https://mods.factorio.com/mod/DeadlockStackingForVanilla . The latter (depending on mod settings) adds recipes to stack 5 underground belts to a stacked underground belt item, and a recipe to unstack a stacked underground belt item to 5 underground belts. Beltlayer infers a recipe from this to unstack a stacked underground belt to 5 underground connectors. And since stacker buildings choose their recipe automatically, you now can't even unstack stacked underground belts to 5 underground belts except by handcrafting.
