If you shoot a zombie's arm off while it's throwing a grenade the aiming reticle sticks, and I think it still acts like it's trying to throw the nonexistent grenade at you.

same thing happens when using the AAL antimasses

Logically it would happen with any held TDExplosive.

Actually, any held item, but TDEx's are probably the only one you typically use.

Also, validating this bug, had it happen myself.

grif, didnt you post this ages ago?

And for the record, it can and will happen to you - if you switch to another weapon, you throw that instead.
(Obviously only if you still have an arm to hold it with)