I've done an upgrade from Umbraco 6.1.5 to Umbraco 7.3.7.

All has been going well, but recently the site has stopped publishing pages. The site is NOT load balanced, but I have suspicions that the recent load balancing changes may have some part to play with my issues.

In the Trace log, I can see the following errors:

2016-02-29 09:03:15,982 [P7628/D2/T51] ERROR Umbraco.Core.Sync.DatabaseServerMessenger - DISTRIBUTED CACHE IS NOT UPDATED. Failed to execute instructions. Instruction is being skipped/ignored
System.Threading.ThreadAbortException: Thread was being aborted.
   at System.Threading.Monitor.ObjWait(Boolean exitContext, Int32 millisecondsTimeout, Object obj)
   at System.Threading.SemaphoreSlim.WaitUntilCountOrTimeout(Int32 millisecondsTimeout, UInt32 startTime, CancellationToken cancellationToken)
   at System.Threading.SemaphoreSlim.Wait(Int32 millisecondsTimeout, CancellationToken cancellationToken)
   at Umbraco.Core.AsyncLock.Lock()
   at umbraco.content.UpdateSortOrder(IContent c)
   at Umbraco.Web.Cache.UnpublishedPageCacheRefresher.Refresh(Int32 id)
   at Umbraco.Core.Sync.DatabaseServerMessenger.RefreshByIds(Guid uniqueIdentifier, String jsonIds)
   at Umbraco.Core.Sync.DatabaseServerMessenger.NotifyRefreshers(IEnumerable`1 jsonArray)
   at Umbraco.Core.Sync.DatabaseServerMessenger.ProcessDatabaseInstructions()

Not I have removed the JSON payload from the error message as it was too big and was killing my browser however an example object from the array is:

{"RefreshType":3,"RefresherId":"55698352-dfc5-4dbe-96bd-a4a0f6f77145","GuidId":"00000000-0000-0000-0000-000000000000","IntId":0,"JsonIds":"[6364,6363,6355,6352,6348,6331,6319,6300,6298,6291,6305,6271,6246,6245,6243,6240,6238,6233,6234,6224,6217,6194,6165,6157,6121,6118,6057,6055,6042,6039,6032,6030,6028,6002,5994,4856,3856,2835,1835,1831,1827,1821,1816,1807,1801,1787,1785,1782,1779,1774,1741,1728,1726,1723,1705,1698,1687,1677,1675,1661,1645,1628,1572,1555]","JsonPayload":null}

I do see that the GuidId is all 0's which I'm not sure is right or not.

And as it may be a load balancing type thing, I can confirm distributedCalls is not turned on in my umbracoSettings.config (though I know this is not needed with the recent load balancing changes)

<distributedCall enable="false">
    <!-- the id of the user who's making the calls -->
    <!-- needed for security, umbraco will automatically look up correct login and passwords -->
    <user>0</user>
    <servers>
      <!-- add ip number or hostname, make sure that it can be reached from all servers -->
      <!-- you can also add optional attributes to force a protocol or port number (see #2) -->
      <!-- <server>127.0.0.1</server>-->
      <!-- <server forceProtocol="http|https" forcePortnumber="80|443">127.0.0.1</server>-->
    </servers>
  </distributedCall>

I have also looked in my DB and can see rows getting added to the UmbracoCacheInstruction table and aren't getting removed.

Has anyone any suggestions as to what may be wrong or what I could try to fix? Not being able to publish is quite a problem to have :)