Ra causing elemental downs with rifle?

Just had a Veteran Thunder Banshee I was fighting suffer an elemental down. I didn't see anyone else on screen or map within range to attack (couple of dots popping in and out of the nearby Ryuker Device), nor any fire techs going off. I was playing Ra/Fo using a carryover Rivalate Rifle, no status affixes. Started the fight by dumping Homing Darts into it until all the legs broke then fired charged and uncharged Razing Shot along with counter shots until it suddenly caught fire. Nuked it with a PB after that.

As far as I know, Ra isn't supposed to be able to light things on fire. The only things I can think of in that fight that might have are Razing Shot's explosions maybe being fire damage, possibly the Rivalate potential actually adding +20% elemental down even to non-elementals, or a caster with massive lag not registering on my screen. Does anyone have information on this?

Went and did some more testing, and it seems to be the Rivalate weapon. I'm getting different status effects on other enemies too if they don't die first. Also lends weight to the idea that elemental downs are weighted by number of hits dealt (or by each PA type), since I never had this on Hu with a sword but get it a lot spamming Homing Darts.

Edit: It's surprising that they actually mean +20% to all down stats, even if it's zero at base. Pretty useful.