Sometimes the "leveling up" sound cue doesnt play for enemies.

I'm posting this in Gameplay because I don't think it's a bug or anything, but recently I sometimes don't hear any sound cue when my enemy laner is leveling up. I'm not sure what's causing it to not play. Sometimes it does, sometimes it doesn't. I guess it has to do with the range, as it feels as though It only plays when the enemy is near the center of my screen. If he is near the border of my screen, he level up without me hearing anything.

I often get surprised by that in early laning phase. I start trading with the enemy laner only to realise that I've made a huge mistake because they just turned lvl 2/3/6 without me noticing as I was expecting to hear a sound cue.

Am I the only one experiencing this ? I only started noticing this recently, was there a change in the way sound cue are played or am I imagining things ?