Fix WordPress Admin Conflict

My WordPress dashboard has become almost unusable—key fields inside wp-admin either refuse to load or stop responding entirely. I suspect a theme conflict combined with a version mismatch, but I haven’t updated the core, the theme, or any plugins recently, nor have I installed or activated anything new.

I need a WordPress specialist to:
• Diagnose why the wp-admin fields are missing or frozen
• Resolve the underlying theme/version conflict without data loss
• Verify that all standard admin functions (editing pages, saving settings, uploading media, etc.) work smoothly again
• Provide a brief summary of the changes so I can avoid the issue in future

Please be comfortable with typical debugging tools (WP-CLI, error logs, database access, safe mode, etc.) and be ready to work directly on a live environment or guide me through a staging setup if preferred. The end goal is a stable, fully functional dashboard.