1. Pick Undying and level up Decay
2. Cast Decay on some enemy heroes to get some stacks
3. Get Aghanim's Scepter

Result: The Decay stacks on Undying immediately update to 10 strength. The Decay debuffs on enemies are unaffected and stay at 4. Vice versa when dropping the aghs.

Expected: Decay stacks do not change upon picking up or dropping Aghanim's Scepter.

The debuff works fine, it stays at 4 or 10.

Another small issue: When Undying has Aghanim's Scepter, the status debuff on hit enemies still says "Losing 4 strength.", instead of saying "Losing 10 strength."