Offline Map Sync Error: Job error 6004 \"invalid start of json - expecting { or [\".

Question

I get this error on a regular basis when syncing an offline map.  I have noticed it seems to occur when I sync soon after opening a map, and before I have loaded the map into a MapView.  I do check to confirm the map and all layers have a LoadStatus = Loaded.

{
	"isServerMessage": false,
	"message": "Layer result: Sync failed. Name: LayerName LayerID: 9 TableName: ... URL: https://services3.arcgis.com/..../arcgis/rest/services/..../FeatureServer/9 Job error 6004 \"invalid start of json - expecting { or [\". < : 0.",
	"severity": "warning",
	"timestamp": 1605810526949
}

The was this post a couple years ago: https://community.esri.com/t5/arcgis-runtime-sdk-for-android/quot-invalid-start-of-json-expecting-or-quot-when-updating-100-1/td-p/690089

But no resolution ever presented

imritanshu · Answer

I am getting same error in fieldmaps android version 22.0.1 Build 1050.

Can anybody suggest is there any limitation of number of layers or the area?

@MichaelBranscomb

JoeHershman · Answer

I added this to occur in my processing which seems to resolve the issue, not really excited about it as a workaround, but for now will have to do

private bool _firstSync = true;

private async Task InitialzeTokens()
{
	if ( !_firstSync ) return;

foreach (var featureLayer in _map.OperationalLayers.OfType<FeatureLayer>())
	{
		var pars = new QueryParameters {WhereClause = "1=0", MaxFeatures = 1};

if ( !(featureLayer.FeatureTable is GeodatabaseFeatureTable gdbFeatureTable) ) continue;
		if ( gdbFeatureTable.Geodatabase?.Source == null ) continue;

var serviceFeatureTable = new ServiceFeatureTable(gdbFeatureTable.Geodatabase.Source);

try
		{
			await serviceFeatureTable.LoadAsync();
			var _ = await serviceFeatureTable.QueryFeaturesAsync(pars);
		}
		catch (Exception)
		{
			//_log.Error(e, e.Message);
		}
	}

_firstSync = false;
}

JoeHershman · Answer

So I tried this with the change that I first log onto AGOL prior to the sync, in that case I see similar results except it never actually goes into the ChallengeHandler.  I was thinking maybe it has to do with the WebMap, but I tried with another WebMap and seems to still have the issue.  I am having a hard time with no one being able to duplicate with this happening every single time I try a first sync.  I am willing to share the code, privately, if someone is willing to do that.

app.log 4.zip

ArcGIS runtime SDK test.zip