Hi,
Thanks for the reply really appreciate it.
Unfortunately I am unable to provide any form of visuals to support what I mentioned. Am only able to provide pretty much the turns and actions.
I will start off with Ferrothorn being swapped in
Turn 1: Swapped out Donphan into Dragonite, Ferrothorn uses Stealth Rock
Turn 2: Dragonite uses DD , Ferrothorn uses leech seed
Turn 3: Expecting a thunder wave and knowing that lum berries usually clears it I decided to do another DD to potentially OHKO ferrothorn with fire punch. Ferrothorn uses thunder wave and the lum berry does not activate.
Once again thanks for the replies, would continue observing if I would to encounter such an issue again.