With custom export, the "Overwrite existing file(s)" checkbox has no effect.
Fix: https://github.com/phpmyadmin/phpmyadmin/commit/afb393816dd2fcc8b1ddb402d644d8cbafe6e157
Fix:
https://github.com/phpmyadmin/phpmyadmin/commit/afb393816dd2fcc8b1ddb402d644d8cbafe6e157