Based on the graph diff in the error message, the issue seems to be that one invocation of your module by the tracer calls self.SqueezeUpsample[2] and self.SkipConnections[2] but the next does not. But I cannot pinpoint in your code where this might be happening. self.SqueezeUpsample and self.skipConnections are used in for loops, but those loops have a deterministic number of iterations…