Problem with objects detection at YOLO then change model

[Lepiloff]

Then I run detection with yolov3.cfg , yolov3.weights and coco.names (80 class list) all working good at video and images, and accuracy too fine. But if I change cfg to yolo3_openimages.cfgweights to yolov3-openimages.weights and openimages.name(601 class list) accuracy is so bad. At the images and videos all classes are generalized. Bee like animal, horse like enimal cars like vehicles and many other objects are not recognized.

I tried to play with NMS IoU threshold, changed from 0.2 to 0.9 (default 0.4) but unsuccessfully. May have tips why such a bad accuracy on pretrained models and config from official repo?