I've been experiencing a consistent bug-(though I'm not sure if its something that happens with other Melee weapons yet, so I listed my exact weapon and skin)-where Melee Influence proc'ing will cause my Warframe to start holding the weapon upside-down in a reverse-grip-(attached below)-until the next Tennokai hit. This causes animations to look horribly janky and I hope this gets fixed immediately.
https://imgur.com/a/3bHUK6i