Please note that Keras Examples are primarily meant for demonstrating workflows as noted here 12.

I added a true random cropping function to the code you provided

Not sure what you meant by true random cropping function.
Is your backbone architecture the same as the paper? The original one is ResNet-18. Even if that is the case, you’d need to ensure it’s following the same hyperparameters (like zero bias in the BatchNorm layers before the identity, etc.).  Following what’s noted under the supplementary A. Implementation Details section is important here barring the CIFAR-10 specific changes.