Hi Shriram, issue is happening because the Validate Card button in the iframe is calling a Mendix published API using a different or anonymous session. When that API call hits, Mendix creates a new session or client instance, which causes the original session on the parent page to expire. That’s why buttons like Back stop working.
To avoid this, make the published API anonymous or route the API call through an external middleware instead of calling it directly from the iframe. This prevents any session conflict and keeps the Mendix client stable.
I hope this one helps you! :)