Issue with OAuth authentication behind IIS

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Question

Hello,

I am encountering an issue with OAuth authentication when running my application behind IIS. The authentication works perfectly in localhost mode (without IIS), but as soon as IIS is involved, I receive the following error in the logs:

Conversion from JSON failed with error: Error parsing NaN value. Path '', line 1, position 1.

I have double-checked my configurations multiple times, and they seem identical between the localhost and IIS setups (aside from the endpoints, which are different).

Do you have any suggestions or tips to debug this issue? Could this error indicate a specific misconfiguration or compatibility problem with IIS?