How to fix the Slayer bug with Steam-Mac users:
Step 1: Remove Slayer if it is not already in your addons folder
Step 2: Download Slayer v3
Step 3: Put Slayer v3 in your addons folder
Step 4: Launch Blockland and update Slayer to the current version
Keep in mind I don't know if this will work for everyone, but it worked for me.
Credits to LegoPepper for helping me solve the issue