An item (e.g. ender pearl) does not render properly when on cooldown. I have tested this with IF and without IF only. No other mods were used in testing. Build of IF I used is the one you provided to me that disabled fast buffer upload optimization on macOS.
With IF:

Without IF:

Log with IF: https://mclo.gs/O9AuIyY
Log without IF: https://mclo.gs/GOANb2V
A lot of the log spam is due to a Hypixel bug.

Fixed in latest dev build: https://github.com/RaphiMC/ImmediatelyFast/actions/runs/11581141931