Massive lags when loading new tile with tiled landscape during gameplay


I am having problems with my tiled landscape. I am using 1009 x 1009 tiles, and when game needs to load one of them during gameplay, there is a huge FPS drop. My landscape is 9x9 tiles and 14.5x14.5 km. Do I need to use smaller tiles, but much more of them? Or maybe it is my terrain material. I have 10 layers, but they are very simple. Normaly I have something around 100 FPS with tiled landscape’s LODs included. Or maybe I need to load all levels before game starts? What may cause this problem? Any tips or advices? Thank you.

Any answers to this?

I have 11,709 tiles in 1009 resolution and have never even seen this problem occur.