Oil grenade not propagating ignite

Sometimes oil grenade doesnt seem to ignite enemies, despite them standing on it, Im not sure how to replicate it but when you shoot more oil grenades on the ground, the ignited ground from that will also not do any damage. I tested it out with 1, 2 and 4 grenades and it seems to happen no matter how many projectiles.

In this image, I am hovering over an enemy in the burning ground that doesnt have ignite on them.

Upon further testing, I believe that the burning ground sometimes inherits the initial ignites duration.

Video of an ignite making burning ground from another burning ground source but does no damage.

https://imgur.com/a/6Ez7j8l

In this one, theres a part in the middle where the enemies stop taking damage, and are not ignited, until another oil grenade explodes.

https://imgur.com/a/o0GzQT8