Why did Flamethrower make my Bastiodon flinch?

Question

I have no saying in this but, When I was battling a Pyroar and with my Bastiodon paralyzed, (don't ask why)
when I was about to use Metal Burst on the Pyroar, it used Flamethrower and, for some reason, it flinched.
I don't know why, can someone help, please?
Thank you.

Comments

Were you online? If you were, the Pyroar could of been hacked (just an assumption) to have Stench.

Stench description (on this site): A Pokémon with Stench has a 10% chance of causing the opponent to flinch when hit by a damaging move (provided the ability-bearer strikes first as usual).

Stench does not stack with the items King's Rock or Razor Fang, so an ability-bearer holding either item will keep the flinch chance at 10%.

Answer 1

The opponent probably was holding a King's Rock.

The King's Rock (Japanese: おうじゃのしるし King's Symbol) is a type of held item introduced in Generation II. It allows Poliwhirl and Slowpoke to evolve into Politoed and Slowking, respectively, and also allows the holder's moves to cause Pokémon to flinch.

Source