Glitchy Mega Gnar hitbox when W (?)

ARAM vs I was Vi. There were 2 cases seem to relate to glitchy Mega Gnar hitbox.

1st case Vi Vault Breaker(Q) through Mega Gnar. Gnar had been transformed into Mega Gnar for some time. Vi Vault Breaker(Q) toward Mega Gnar, yet didn't knockback Mega Gnar but hit Soraka at the back kb her so. I have no idea if Mega Gnar took the damage. Right within a second Mega Gnar had Crunch(W) to Ezreal, etc. at the back. What I assume is that Mega Gnar's Crunch(W) had been registered when Vi's Vault Breaker(Q) hit the visual Mega Gnar. But this would be some huge visual lag.

2nd case Vi Assault and Battery(R) on Mega Gnar, Mega Gnar Crunch(W) away, no knockup, Vi didn't follow to Mega Gnar's location. Gnar had been transformed into Mega Gnar for some time. Vi Assault and Battery(R) targeting Mega Gnar. Vi had been guided toward Mega Gnar. During the "Guide/Dash", Mega Gnar Crunch(W) to somewhere. Vi didn't "guide/dash" following Mega Gnar, instead Vi kept course and performed her "knockup" trick at the original Mega Gnar's location. Mega Gnar didn't get knocked up. I have no idea if Mega Gnar took the damage.