Rengar empowered E on CDR after normal E is on CD sometimes

Hello, I am a rengar main, I'm not sure if this bug has been reported yet but when playing rengar I found that sometimes if I used E to get to the 5 ferocity stack, the empowered e comes on the same cool down clock as the normal bola. It's really annoying as ganking champions or running away, the snare being delayed for 4-5 seconds really makes a difference.