There is a small chance when throwing a grenade it won't actually throw a grenade. So you had to do the whole animation again to throw it.
#Grenade Bug, Had to Throw Twice
kind obsidian
torn parrot
quartz grotto
round bridge
Slightly different thing, but I’ve also noted that a grenade throw usually cancels when you die, even after having pulled the pin. I don’t remember it always being like that
twilit cloud
Slightly different thing, but I’ve also noted that a grenade throw usually cance...
You used to drop it if you died after pulling the pin.
I think there's a chance whatever they did to make mines and C4 not be placed unless the animation has played all the way is affecting grenades.
It's a bit of a stretch, but it's also a weird coincidence that makes sense with what you said