Fine Tunning Model at step 0 detects nothing

[seannyfeng]

I have been tring to fine tunning a pre-trained model with my own dataset.

I have changed "fine_tune_checkpoint to point" to the downloaded ckpt and "from_detection_checkpoint" to true

However, it seems that the training process wiped out all the pre-trained weights and started from scratch, because when I use the checkpont generated at step 0, it cannot detect anything.

The pretrained model I have selected is faster_rcnn_inception_v2_coco.
I have also tried rfcn_resnet101_coco, same problem.

Another thing I have noticed is that the downloaded ckpt is about 52099 KB, but the checkpoints during training is about twice the size (100596KB) and after exported to inference_graph, the size reduced to again to similar size (50337KB)...
Can anyone please shed a light on this size change as well?
Thank you in advance!

System Info:
Ubuntu 18.04.2 LTS
Python 3.6.9
Tensorflow 1.12.0
CUDA 9.0
CPU i9-9920X
GPU TITAN RTX