You are far from alone mate. The most pronounced NetEnt lags actually happen the other way around. During respins on games like King of Slots, Reel Rush, etc it is actually the losing spins that lag.
But NetEnt are not alone in this kind of thing. Microgaming and iSoftbet for example have their own lag on a lot of games when 2 scatters are going to land on reels 1 to 4.
Then some Playtech games have their own quirks as well with the scatters.
This is all completely useless to a player but something we enjoy spotting and writing about.
