To help answer your questions:
What mode is your form in? DefaultMode = FormMode.Edit
Are you sure that when you select an existing record to edit that the form is being set to Edit Mode rather than New? OnSelect = EditForm(EditForm_Bridge);Navigate(EditForm_Bridge)
when clicking the chevron arrow on the browse screen gallery
What is the OnSelect code for your submit button?
OnSelect = SubmitForm(EditForm_Bridge);Navigate(BrowseScreen_Bridge)
What is the code in the update property for your datacards?
Update = DataCardValue132.selected for my "Review Status" which can be selected 'Pending' or 'Complete'
Honestly I am not sure where the 132 is coming from.
It appears that "Person or Group" field will not allow updates. My date fields can be edited and the changes will save. But I try to change the "person or group" and it does not change when I hit the save button to submit the form. Even when I choose "Pending" as my status, the person or group change will not save. My status field is a choice field for "pending" or "complete".
I can actually edit the record in Sharepoint directly in my list. Then the changes are saved. However, if I try to edit in the PowerApp, then it will not save the changes.
Does that make any sense? It is weird. I have been using this PowerApp that I made since last October and never noticed this. I was expanding the use of the app and noticed this anomaly.