Accounts error when loading in Outlook client, off line mode

I have a problem with Outlook offline mode (CRM2016 Update 1 Online, using CRM2016 Outlook client).

Contacts and custom entities are working correctly. They show off line and can be edited. Including inserting / updating notes!

But as the account form loads we get the following error and the form never displays.

Does anyone have suggestions as to possible causes?

Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #4F4BA701Detail:

<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">

  <ErrorCode>-2147220970</ErrorCode>

  <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />

  <Message>System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #4F4BA701</Message>

  <Timestamp>2016-12-19T11:52:23.4854284Z</Timestamp>

  <InnerFault>

    <ErrorCode>-2147220970</ErrorCode>

    <ErrorDetails xmlns:d3p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />

    <Message>There was a problem while trying to set value for "SelectDefaultLanguage" parameter of the control with ID = notescontrol

One of the following may have caused this exception:

1). The property does not exist on the control or it is not public.

2). The property is not writable.

3). The property is not marked with the CrmControlParameter attribute.</Message>

    <Timestamp>2016-12-19T11:52:23.4854284Z</Timestamp>

    <InnerFault i:nil="true" />

    <TraceText i:nil="true" />

  </InnerFault>

  <TraceText i:nil="true" />

</OrganizationServiceFault>