Running a var_dump on the $value before and after the foreach loop in update_value shows that the value is the same before and after. Trying to save one relationship field with one post selected gives me this: array(1) { [0]=> string(1) "8" }
As I mentioned earlier, the value can be set without The Events Calendar activated and, when activated it hides the values and doesn’t allow updating but also doesn’t delete the values. When you deactivate it again, the values selected before activating are back and visible.
In addition, this also effects the_field()/get_field() which similarly cannot access the value stored in the DB when TEC is activated even though the data is still there.
I’ll dig some more…
