Finishers use current weapon instead of melee weapon

[Noctah]

Very often, doing a finisher will make my warframe smack the enemy with their equipped gun (mostly primaries) instead of using its melee weapon.

I've noticed it the most often when I play Excalibur Prime and using the Burston Prime/Nikana Zaw, but I've seen it happen regardless of my loadout (Hammer, Heavy Blade, Opticor...)

Not sure what causes it, but if it bugs out once, it will bug out for all subsequent finishers.