Slashmolder
'Ello Governor
Could you please post which seed you are using.I'm trying to fish a female Rash Dratini with perfect IVs. *snip* Is there a difference between catching Pokémon in grass with cathing them by fishing or surfing?
The most likely cause is that NPCs are advancing the PIDRNG making you off.
There is a difference between the methods but if you selected the correct method you should be fine.