@xh I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.
Issue:
Resolved by @xh
According this thread learn.microsoft.com/en-us/answers/questions/1184652/…, i modified spring source code to skip signature verification for SLO response