Here's what I did, and it was working fine for me:
I took your same basic schema (except I had a days node around the repeating day node).
Then I added two fields: day_id_seed, and detail_id_seed. I set both of these to a default value of 1.
For day_id... I set the default value to day_id_seed (and unchecked update value when result changes check box). I added a rule to update day_id_seed to this nodes value + 1.
For detail_id... I set the default value to detail_id_seed (and unchecked the update value when result changes check box). I added a rule to update detail_id_seed to this nodes value + 1.
Then I added all the fields and repeating sections to the view, and previewed... everything worked as expected: inserting randomly, deleting rows, etc.
Hope this helps.