Update shader is taking longer after each frame. From 0s in frame 1, to 10s in frame 33 and so on. It's simple nature scene, each material has simple shader for alpha transparency (4 nodes). The same with rendering images frames or movie file. There are 3 scenes in this file.
File: 50 samples, 720p, tiles 512x512, 1 source of light (sun), default denoise, 1 light bounce, gpu compute.
Specs: win 7 64, gtx 1050ti 4gb, 4gb ram, amd phenom 970