Theme Changes Only Work After Uploading a Cover Photo

When I try to change the forum theme, the selected theme is not applied immediately and the forum continues to display the default theme. However, if I go to my profile and upload a cover photo (or make any profile-related change), the theme I previously selected suddenly becomes active and starts working correctly.

This behavior suggests that the user's theme preference may not be properly updated in the database, session, or cache system when the theme is selected. When a profile update occurs, the user cache/session appears to refresh, causing the saved theme preference to be applied correctly.