I think the error is due to the fact that we ignore the placement of quant-dequant nodes in the model in the logic that raises this error. Since the global qconfig is used, it raises the error as it expects the ConvTranspose to be quantized using same qconfig. I have filed ConvTranspose config error in prepare API · Issue #57420 · pytorch/pytorch · GitHub 10 to track this.
To avoid this error can you try setting the qconfig of all the ConvTranspose modules to None? Hopefully, that should fix it.