Description:

• When adding speed module on Industrial Smelter or Condenser, the module can be stackable. It's not the case for machine upgradable (MK1 to MK4)

Steps to Reproduce:

• Place an industrial Smelter or a condenser, put energy in it.
• Place a speed module
• Add another one by shift clicking the second one
• See that it's stacked with the first one.

Technical Information:

• Minecraft: 1.17.1
• Fabric API: 0.12.5
• Industrial Revolution: 1.12.0
• Modpack: AOF4 1.1.0

Logs:

• No Log -> No Crash.

Details:
Extra information that might be helpful like screenshots or technical information about your computer.

It's per design. I've seen the tooltips too late. Sorry for the issue. :)