I just noticed an issue that has been present in Collector and appears it happens in this new app as well.
1. Hosted feature layer with editing enabled, sync enabled.
2. Add to map. Make a copy of the layer in the map, add a filter, symbology, etc. to the copy of the layer.
3. Create offline area.
4. App only downloads "one" layer in the map. The copy is not downloaded.
As a workaround, we had to create a hosted view, go through setting that view up with symbology and filters for reference, and adding the hosted layer and hosted view into the map. Then it downloaded and worked as it should. I remember this issue being in all the Collectors (Classic and new) where if you have a copy of a layer in your web map, the copy didn't work - whether downloaded offline or just loaded directly.
Please look into and fix. Kind of disappointing to see legacy issues from Collector (some a couple years old now) present in a "new" app. If I run into all the same problems in field maps as I did Collector, I see no reason to be pushed into changing. And we can't really wait another 2 years for these issues to be worked out. Data collections and field seasons continue regardless if Esri software is working or not.