Base information

• Minecraft version: 1.16.5
• Mod version: 3.0.27.462
• Minecraft Forge version: 36.2.39
• Mod Pack: N/A

Description / steps to reproduce

Step 1: Start Minecraft
Step 2: Join in the world
Step 3: Build Fusion Crafting construction
Step 4: Right-Click to Fusion Crafting Core

Result: One or more injectors are too close!

You need at least 2 blocks between the core and the injectors.
Also the error message in the GUI won't go away until you place something on one of the injectors.
That is a minor bug.