Grenades sometimes not detonating

Using Gas Grenades, noticed a whole lot of times where the grenades would land on the ground and just not detonate at all.
Not sure if this also occurs with other grenades but it would happen semi frequently and I'm not even past act 2 on this character yet.
Very frustrating for obvious reason.

I think it might be something to do with thinking that the grenade has not 'landed' but not sure.