NPC walking in grass makes grass rustling appear for the player as well

[Courtland]

I have a trainer walking within the grass, and it triggers the grass rustle animation for not just him, but the player as well. So, I could be on normal ground, while the trainer is in the grass, but it triggers the rustle effect on both of us. But not vice versa?

 

[Maruno]

Since you haven't told us what you've done to your game, all I can say is that this doesn't happen in Essentials.

 

[Courtland]

To be honest, I have no idea why this would be happening. I have a custom tileset, with the correct terrain tags and what not, but it's still happening. I even tested this same thing with the default tile set "Outside", Gen 1 on a different map, but the same things is happening. So I guess that means it's clearly something I did, but I only added scripts, graphics and tile sets to my game. So what could possibly be the problem?