I feel like it’s a Roblox render bug, this also happens when many transparent parts are placed behind each other, causes them to z fight. Decals tend to do the same sometimes, don’t know why, just know it’s a Roblox graphics thing.
Edit: Don’t know if they’re already working on it but I hope Roblox fixes this Z fighting bug with decals and transparent parts, I’ve had issues with it myself as well.