Same problem here, debugged this into the issue with PHP 8.2 + Polylang which causes an error “cannot call translate on null” on line if ( $mo->translate( $old_values ) === $values ) { in polylang.
TLDR: if polylang related try adding
// Disable some Polylang filters to avoid errors during the process
global $wp_filter;
foreach ($wp_filter as $hook_name => $hook) {
if (isset($hook->callbacks)) {
foreach ($hook->callbacks as $priority => $callbacks) {
foreach ($callbacks as $callback) {
if (is_array($callback[‘function’]) && isset($callback[‘function’][0]) && $callback[‘function’][0] instanceof PLL_Translate_Option) {
$wp_filter[$hook_name][$priority][] = $callback[‘function’];
remove_filter($hook_name, $callback[‘function’], $priority);
}
}
}
}
}
After switch_to_blog(1); in file duplicate.php
