Desktop Mode: Parent-to-Child Form View Bug?

[dustwhit]

Hello, has anyone had problems with their Desktop mode not correctly allowing child rows to be added to a linked parent table?

I have a Unit table (parent) and an Item table (child). On the form view of the parent table, I have the Related Items column so that I can add new child entries from the parent (has previously worked well until about a month ago [desktop mode], and still works correctly on mobile. 

When I add the first child, everything seems normal and I hit save:

I believe the child is correctly processed, and then it opens a second screen where things go wrong (see how the layout has changed? its no longer split in from the right, but takes up the whole screen). This form now locks me out of going back to the parent.

If I hit "Cancel", it prompts me to discard everything and I'm back to the beginning, unable to add children from the parent. This UI behavior has changed from something recent. The button that I normally use to go back to the parent after adding a child has gone away.

I appreciate any thoughts.