Slit_bodmod

I have been working on a mod for 1.15.2 Minecraft, I am new to Minecraft mod development. I thought I had a grip on how tags worked however whenever I try and append some items in my mod to a Minecraft tag it seems to somehow stop that tag from loading any items either from vanilla or my mod. I haven't (yet) tried to access or manipulate any files in code or access tags at any point, in theory it should be a resources only problem. I haven't deliberately overwritten any Minecraft data files although I have overwritten textures for horse armour and dark oak leaves. I have made sure that my files are in the right place and that the replace setting is set to false. As an example I uploaded my extension to the walls file saved at src/main/resources/data/minecraft/tags/blocks/walls.json. The intended result was to let my thatch, blackstone and blackstone_bricks wall connect to other walls in the game however the effect has proved to stop any walls from connecting to any other walls while the game is running. No recipes are working, leaves are decaying next to log blocks it's all gone a bit disastrous. Any help would be much appreciated as like I said, I'm relatively amateur, thought I had a grip on things and now really don't know what to do. walls.json