Often times issues at the SI joint can be linked to a tight anterior hip/lack of hip extension. The quadratus lumborum (QL) is often tight as well, which can cause an upslip of the ilium. I’d try working on these two areas to see if they are contributing to the issue.
For the anterior hip couch stretch is a great go to:
Also try an SI joint reset :
Here is another great video going over an overview of SI joint pain:
Hope that helps! Let us know how it goes.