I also ran to the same problem, for my case the model uses batch norm heavily in different layers. I poked around the code, I think the problem might come from track_running_stats ( line 64 in this file: https://github.com/pytorch/pytorch/blob/master/torch/nn/modules/batchnorm.py 261 ).
I solved the problem by setting the track_running_stats=False for all batch norm layers in the model. This is due to a bug I think in line 64 of the above-mentioned file.
if you want the model to work in eval mode, simply set the track_running_stats to False for all batch norm layers:
for child in model.children():
    for ii in range(len(child)):
        if type(child[ii])==nn.BatchNorm2d:
            child[ii].track_running_stats = False