Drupal - View Field disappears when page is saved

Question

We've got some pages on our Drupal 8.4 site (Program pages) that are supposed to show a list of courses in their program. After upgrading, the course list will disappear any time these pages are saved. Our setup involves 3 separate content types:

1. Program Pages, which have a view field that uses a filter to get courses belonging to its program, called field_program_courses. This is what disappears.
2. Programs, which contain info on a program and have an Entity Reference field indicating which Program Page they're linked to (field_program_page_to_link).
3. Courses, which have information on courses, including which program(s) they belong to (field_select_specific_program).

Since upgrading from Drupal 8.1 to 8.4, any time we click "Save" on a Program Page (even without making any changes) causes the database entry for that Program Page's field_program_courses to be erased, and stop showing up when the page is viewed. We must go back to a previous revision for it to show up again.

If I create a new Course, it will display fine on existing Program Pages, but if I try creating a new Program Page it won't show any Courses. I tried creating a new View to replace field_program_courses, but it won't allow me to select field_program_page_to_link in the relationship dropdown, so I can't get proper filtering.

Sadly this seems to have been caused by the update to Drupal 8.4, and rolling that back isn't an option. Any ideas, questions, or suggestions on how to proceed?

Answer 1

Ended up turning to a contractor to resolve this. They said the issue happened because the field_program_courses field has a hook that loads a list of views. That stopped working, so the only selectable option became "none", so saving the page of course used the "none" value. As for why exactly it stopped working, their guess is that it was caused by a change in the field_block contrib module in the 8.1->8.4 upgrade, though they're unsure exactly what it was.

The fix involved re-creating the view with another display that didn't have the contextual filters, and adding some code to our theme which loaded the block for Program Pages.