What you were expecting to happen, and what actually happened:
As shown on screenshotbonus damage says +112 this should be +10 in this case since it’s a bonus of +10 for each brown enemy
How often does this happen? When did it begin happening?
every time
That’s how it is. Notice that apart from boosted damage, spell does 0 damage at all.
(try casting sylph once it’s entangled and no brown troops on enemy team - it will literaly do nothing).