Version: 1.21.1 NeoForge

Without ImmediatelyFast:

With ImmediatelyFast:

Upload the game log and steps needed to get the Magic Cast Meter HUD element to appear

I'm experiencing the same thing.
Here's how to reproduce it

1. install DragonSurvival and ImmediatelyFast together.
2. after entering the game, cast any dragon skill. - Hold down the shortcut for casting the dragon skill for 2-3 seconds.
3. The skill casting bar will not display properly, but the skill will execute correctly.

Attach a log of the process.
https://mclo.gs/RhqCOEI

This issue is fixed in the latest dev build: https://github.com/RaphiMC/ImmediatelyFast/actions/runs/14149227051