Forge: 31.2.36
ILikeWood: 1.15.2-2.2.2.0

The Biomes O Plenty wall types, such as Magic wall and Cherry wall, do not attach to each other at any angle. The vanilla walls, Birch etc, are perfect

See pic: https://imgur.com/a/9FFfq5c

do you have the datapack for BoP installed? :P

Well that fixed it. I just assumed the datapack was for recipe changes.

Thank you

I use my own datapack to adjust recipes/loottables and advancements - I've copied the minecraft/tags/blocks/walls.json to my datapack and all is working fine