In this case it is the HSL filter. Here only the head of the snake should be desaturated. In Photo 1.8.4 it works as intended. In beta 1.9.0.199 also the shadow under the snake suddenly disappears. See videos.
Cheers, Puck
Bildschirmvideo aufnehmen 2020-09-29 um 10.05.13.mov
Bildschirmvideo_aufnehmen_2020-09-29_um_10_06_39.mov