The Group Policy Client Side Extension Folder Redirection was unable to apply one or more settings because the changes must be processed before system startup or user logon. The system will wait for Group Policy processing to finish completely before the next startup or logon for this user, and this may result in slow startup and boot performance.

Has anyone seen this?

Log Name:      System
Source:        Microsoft-Windows-GroupPolicy
Date:          17/09/2019 07:32:02
Event ID:      1112
Task Category: None
Level:         Warning
Keywords:      
User:          DOMAIN\%username%
Computer:      PC.DOMAIN.local
Description:
The Group Policy Client Side Extension Folder Redirection was unable to apply one or more settings because the changes must be processed before system startup or user logon. The system will wait for Group Policy processing to finish completely before the next startup or logon for this user, and this may result in slow startup and boot performance.
Event Xml:
<Event xmlns="http://schemas.microsoft.com/win/2004/08/events/event">
  <System>
    <Provider Name="Microsoft-Windows-GroupPolicy" Guid="{AEA1B4FA-97D1-45F2-A64C-4D69FFFD92C9}" />
    <EventID>1112</EventID>
    <Version>0</Version>
    <Level>3</Level>
    <Task>0</Task>
    <Opcode>1</Opcode>
    <Keywords>0x8000000000000000</Keywords>
    <TimeCreated SystemTime="2019-09-17T06:32:02.570830500Z" />
    <EventRecordID>496583</EventRecordID>
    <Correlation ActivityID="{B28BB7AA-31D7-499F-8CCA-B10BC642B36D}" />
    <Execution ProcessID="1112" ThreadID="3604" />
    <Channel>System</Channel>
    <Computer>PC.DOMAIN.local</Computer>
    <Security UserID="S-1-5-21-4190174087-632213676-3596977503-1197" />
  </System>
  <EventData>
    <Data Name="SupportInfo1">1</Data>
    <Data Name="SupportInfo2">4432</Data>
    <Data Name="ProcessingMode">2</Data>
    <Data Name="ProcessingTimeInMilliseconds">1217</Data>
    <Data Name="ErrorCode">1274</Data>
    <Data Name="ErrorDescription">The group policy framework should call the extension in the synchronous foreground policy refresh. </Data>
    <Data Name="DCName">\\DC1.DOMAIN.local</Data>
    <Data Name="ExtensionName">Folder Redirection</Data>
    <Data Name="ExtensionId">{25537BA6-77A8-11D2-9B6C-0000F8080861}</Data>
  </EventData>
</Event>

On a Windows 7 Pro PC connected to a Windows 2016 Foundation server network - upgraded from SBS2011

The redirected folder policy - does it need to be re-made to get rid of this or can we delete the old redirection policy from Group Policy somewhere?

You can reconfigure this from the server dashboard in Windows 2016 Server Essentials.

If you wish to just disable it, you can do that in the dashboard too.

Also use the group policy analyser to check that no unavailable resources are being referenced in any of the policies. It is a simple tool to use and comes as part of Windows. It also gives you a nudge to update or remove any policies that may be put of date.