There were two `RESNETS` sections, which overrode each other, leading to error messages like: 

```
RuntimeError: Error(s) in loading state_dict for GeneralizedRCNN:
	size mismatch for backbone.fpn.fpn_inner1.weight: copying a param with shape torch.Size([256, 256, 1, 1]) from checkpoint, the shape in current model is torch.Size([1024, 256, 1, 1]).
...
	size mismatch for roi_heads.mask.feature_extractor.mask_fcn1.weight: copying a param with shape torch.Size([256, 256, 3, 3]) from checkpoint, the shape in current model is torch.Size([256, 1024, 3, 3]).
```

This just combines them back into a single section, while maintaining all param values. That got the model running again for me.