Invisibility Potions not completed in correct time displayed

When drinking an 8:00 long Invisibility potion, it should last the 8:00. However, at times it cuts out before finishing.

What I expected to happen was...:
After drinking the potion it should last the full 8:00.

What actually happened was...:
Sometimes the potion doesn’t last 8:00. Randomly cutting out

Steps to Reproduce:
1. Brew 8:00 long Invisibility potion
2. Check around the 2-3 mark left of time.
3. Observe when the potion time ends