Bug with Dual Pistols: Incendiary Ammo not consistently applying DoT

[Valcarde]

Currently levelling a Dual Pistols/Martial Combat blaster in Praetoria.

I'm finding that Incendiary Ammo is applying the fire DoT inconsistently; it does not seem to be applying after every attack, as advertised.
Currently powers:  Pistols, Empty Clips, Bullet Rain (Primary), Storm Kick and Reach for the Limit in the secondary.

The two attached files show the combat log for when the DoT doesn't apply correctly, and how the combat log *should* look when the DoT is applied.

City of Data shows it should be applying 100%, and as far as I know, that is how Swap Ammo is supposed to work.