Hoping the submission process is now debugged. It took a while to solve it. For those interested, the new submission issues this year were caused by major changes to WordPress backend and several plugins we used to support the backend in the past year. WordPress moved to Gutenberg backend editing and that required various reconfigurations, plus changes had to be made to theme files, to php variables affected by a server migration in January (to improve site speed), plus debugging PDF viewing, and resolving multiple plugin bugs related to WP Gutenberg’s new (nonexistent) handling of custom fields, which our formerly ‘simple’ submission process relied heavily on. Phew!
Hopefully, it will indeed be simple again going forward. And thanks to all for being patient as I debugged it!