1. Pick Elder Titan, level up Earth Splitter and get Aghanim's Scepter and a Refresher Orb
2. Create an enemy hero
3. Cast Earth Splitter on the enemy hero
4. Use Refresher Orb and cast Earth Splitter on the enemy hero again
5. Now, after the first Earth Splitter implodes, drop your Aghanim's Scepter
6. Wait for the second splitter to implode as well
7. Check for how much the enemy is slowed

Result: The first Earth Splitter placed a disarming and slowing debuff, slowing for 30%/40%/50%. The second Earth Splitter placed only a slowing debuff, because the scepter was dropped, also slowing for 30%/40%/50%. They both slow, so hit enemies are slowed by 60%/80%/100%.

Expected: Multiple casts of Earth Splitter should not stack the slow. This already works fine with 2 non-aghs or 2 aghs splitters, they refresh the debuff. Only when non-aghs gets combined with aghs splitter they stack.

Note: This can be easily abused when having farmed Refresher Orb and Aghanim's Scepter. All the player has to do is to drop his scepter while one of the splitters implodes and have it in the inventory while the second implodes. This abuse can slow even 522 movement speed units down to the 100 minimum.