This is noticable with Aghanim's Scepter when attempting a very long Rupture on one enemy. If you recast it on the same enemy, but level it up before doing so, it does not update the damage percentage to the new level. It only refreshes the duration.

1. Pick Bloodseeker, level up Rupture and get Aghanim's scepter
2. Cast Rupture on an enemy
3. Level up Rupture again
4. Before the Rupture expires, recast it on the same target

Result: The damage percentage is not updated, still using the value of the previous level. Only duration is refreshed.

Expected: The damage value should update to the spell's level on refresh.