Sonikku

So, me and my friends have a server on 1.12.2 forge and we've decided to remove some mods. There comes the issue, whenever I remove a mod, like for example macaw's windows snd start up the server, it just gets stuck, it says missing an registry entry minecraft:blocks: macawswindows:xxx (<-- just an example) The server keeps saying player disconneted, server starting and it never boots up. Then i go to test the world in my singleplayer. When I after some fiddling manage to launch the world in my singleplayer with the mods removed and it works fine, I put it back with the mods removed from the server and my game, it does the same thing again. Missing..