Sync error: Illegal start of token [<]

[PaulBoehnlein]

Trying to sync a feature service with offline edits in Collector and receiving the error "Illegal start of token [<]".  Service has subtypes, domains and editor tracking.  Hosted in a ArcGIS Online web map.  Can anyone help with this?

[MiaogengZhang]

This issue could be related to network. If you are using Web Adapter, try to increased the uploadReadAheadSize value on IIS and sometimes that was enough to fix the issue

1. Launch “Internet Information Services (IIS) Manager”
2. Select the site that you are hosting your web application under it.
3. In the Features section, double click “Configuration Editor”
4. Under “Section” select: system.webServer then serverRuntime
5. Modify the “uploadReadAheadSize” section

[MiaogengZhang]

In iOS, you will meet this error if you have a Server feature service added as an item with stored credentials in ArcGIS Online. The feature service has attachment enabled. Then you add picture attachment made from photo library instead of camera.

[BledarBirbo1]

Sorry.

What does this error have to do with the kind of IMAGE that the user has selected. ?

[WilliamMcInnes]

Is there any way to resolve this error so that the user can sync?

[BledarBirbo1]

Hi William.

We found that a fast network connection (UPLOAD SPEED) can fix this error.

Hope this helps.

[WilliamMcInnes]

Thanks, we are on a satellite connection that can be slow at times. We will try to upload when traffic on our network is low.

[BertKraan1]

Yep, could be network traffic related. I had this while at the same time downloading another map. After that was finished synchronising was flawless.

[ronaldbruzzese]

Miaogeng,

What did you increase the “uploadReadAheadSize” to?

Thanks

[MiaogengZhang]

You can start with ~20MB and adjust it. 

[danbecker]

We have experienced a variety of token related errors on both iOS and Android collector versions, including 10.3.

Unable to download a map for offline use, unable to sync edits made on the device, ect...

In all cases, it was a result of:

1. feature service published on our own ArcGIS Server ver. 10.3

2. feature service credentials stored with the item when it's added to AGOL

Simply add the item to AGOL without storing the service credentials and the "token" problems are gone. Only downfall is having to login to BOTH collector AND the feature service.

We've simply created ArcGIS Server username/passwords to match our AGOL named user accounts, then field staff never get confused. They see a credential prompt and enter the same info.