Please refer to my post in your other thread on the same question:
"You are correct about the problem. It is related to the serialization of the design time values of the data source parameters. We have modified this behavior due to some particular problems when upgrading to a new version of our product.
The good news is that the issue has already been fixed. You can download the latest internal build (126.96.36.1990) from your account and give it a try.
If the described issue is not related to your problem, please elaborate on the problem in the private thread by providing the problematic report file and the exact steps to reproduce the problem.
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