this means you are quantizing a already quantized Tensor, it’s because QuantStub is not placed correctly in the original model, you might have a Tensor being quantized multiple times.]
e.g.
x = self.quant(x)
x = self.quant2(x)
looks like you have quantwrapper over the original model and the fasterrcnn model, this would mean the input of FasterRCNN model is quantized twice.