Combo Box Default Items don't load reliably

[jnickell]

I have two combo boxes on a Power App that are inconsistent on loading the default values. The default items are driven from the previously selected value stored in a Sharepoint List.  The Items source for both combo boxes are DataVerse tables.  One combo box is filtered by the first.  Sometimes on navigating to the Edit page both values are present as expected other times one or both may be blank, most often it seems to be the first combo box.

The PowerApp was created from the Sharepoint list, and the "Edit" screen is where I see the issues.  If I cancel out of the edit screen, go back to the Gallery view, then select a second item, return to the gallery view and then edit the original item both fields are present as I would have expected them to be the first time. 

I've enabled debugging and looked through the Monitor logs and from what I can tell it's only the first trip into the "Edit" screen that generates queries to the DataVerse tables. I don't see a second query to the Dataverse table when you go into the Edit screen a second time. 

Is this a configuration issue on the combobox? What could be causing it to routinely not show both items on the first attempt to browse to the Edit Screen. It may be worth noting that while the Sharepoint list values for both of these fields are shown in the Gallery View, they are not shown on the Details view and it's not until the Edit screen that the DataVerse table values are needed.

Hopefully the table describes the process flow I'm following.

App Load to Gallery	Nav to Item 1 Detail	Nav to Item 1 Edit	Cancel to Detail Screen	Back to Gallery	Nav to Item 2 Detail	Back to Gallery	Nav to Item 1 Detail	Nav to Item 1 Edit
		Combo Box(s) missing values						Combo Boxes have values

Here's the "Default Items" formula for the first combo box:

ThisItem should be the Sharepoint list context.

Filter('Indices','Job Number' = ThisItem.JobNum)

Here's the Default items formula for the second combo box:

If(IsEmpty(ThisItem.MONum),
  Filter('MO Dimensions', JobID = ComboBox1.Selected.'Job Number'),
  Filter('MO Dimensions', 'Manufacture Order' = ThisItem.MONum)
)

 Other than enabling Debugging and looking through the monitor results, I'm relatively new "debugging" power apps.

[Pstork1]

One of the peculiarities that applies to the way ComboBoxes work is that the default only applies until a user interacts with the Combobox.  Once something has been selected the default is ignored until a Reset(control) is issued for that combobox.  Could it be that the defaults aren't being used because something is being selected manually before navigating back to the screen?

[jnickell]

If that's the case, it's Power Apps interpreting part of the page load as an interaction, but that would explain why sometimes upon entering the page the values are "there, but then disappear".

But to your question, the user isn't interacting with the form.

The only button clicks are to "edit" the Details screen and then the Edit screen comes up with missing values.

Where could I look to see if part of the page load is causing this?

[Pstork1]

I would check the monitor. It should report any actions taken on the forms.  Are the defaults set to the values coming from a record or are they hard coded?  

[jnickell]

The default set to values are coming from whatever was stored in the Sharepoint list for that item, so they're not hardcoded to the form. It's basically filtering the Dataverse table to the item that was previously selected.

I'd use the montior, but from what I can see there are no queries logged when I navigate to the Edit page the second time. Only Navigation events are logged.  So it makes it kind of hard for me to identify what the "proper" process is.

Is it normal that you would only see navigation events when you re-navigate to a page, even if the content on that page is different than the last time you were on the page (different information about a different item).

[Pstork1]

You aren't getting queries the second time because data has been cached in the App.  If you need to manually make sure the cached data gets refreshed then issue a Refresh(datasource).

[jnickell]

That semi-makes sense because I was see queries in the initial entry that are hitting the source Dataverse table without the filter, but how do you tell what query is controlling what shows up in the combo box?

[Pstork1]

The queries are for the full data source.  So if there isn't a Refresh of the data source or a reset of the combobox then it will show the last entry.

[jnickell]

Thanks for you input so far. This is beyond troubleshooting that I've done previously with PowerApps, and it seems to be just subject to how the form loads "in that instance"

I was able to get a monitor session that captured a "working" instance, and a "partially working" instance. In the partially working instance the second combo box doesn't show a value, but the first combo box does.  I've downloaded both json files and am trying to use NotePad++ to compare the two. I'm not coming up with anything that points to an for sure root cause.

There are three combo boxes on the form that pull from Dataverse tables using whatever was previously entered in Sharepoint as the "Default Items" search filter.  I've been focused on the first two as they are related and seem to be having the most issues. I've not really been watching the third combo box.

It seems like the page doesn't load the pieces in the same order, and if that's causing my issue how do I control it?

Worked Fully	Only Worked Partially
Line 3487 - Loads Default Items for ComboBox3	Loads ComboBox2 Items
Line 3558 - Loads Default Items for ComboBox2 (empty lookup)	Loads Default Items for ComboBox2 (query has SP item value)
Line 3629 - Loads Default Items for ComboBox1	Loads Default Items for ComboBox1
Line 3700 - Loads Default Items for ComboBox2 (query has SP item value	Loads Default Items for ComboBox2 (an empty lookup)
Line 3711 - Load ComboBox2 items
Line 4024 - Load SearchItems for ComboBox1
	Line 4118 Load SearchItems for ComboBox1
Line 4189 - Load ComboBox2 items	Load Combox2 Items

It seems to be related to the order of the Default Items query, but how do I effectively manage that?

[Pstork1]

If those are all on the same screen I don't think you can control the order in which they load.  It all depends on the connection to the database and everything loads asynchronously.