Error with OData

asmilie2b

WHen running powerpivot with OData in NAV 2013, every couple of days or so, we receive the below error in Powerpivot.

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Errors in the high-level relational engine. The following exception occurred while the managed IDataReader interface was being used: The remote server returned an error: (500) Internal Server Error
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Checking the event viewer on the tier server we see the below

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Server instance: DynamicsNAV70
Session type: UnknownClient
Session ID: N/A
User: mydomain\myuser
Type: System.IndexOutOfRangeException
Message: Index was outside the bounds of the array.

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Restarting the tier service resolves it, but is a little harsh. Has anyone seen this?