@Zafar, I am facing the same issue. It seems to be a Keypoints issue. I trained same model on Keypoints data and classification data ( just last layer changed). I got following results on quantization.
Trained for Keypoints:
Weights SNR: 40 - 47 (almost perfect)
model outputs stats SNR: 23(first layer) - 0.01 (end layers). The value kept on reducing with every layer. Why there is no correlation between weights and output.
Quantized model accuracy: 0.01
Trained for Classification:
Weights SNR: 43-48
model outputs stats SNR: 10-22 (random)
Float model accuracy: 92%
quantized model accuracy: 91.6%
I will be waiting for your analysis.