UTM 9.402-7 failing to connect to up2date servers

Question

My home utm has failed to connect to the up2date servers for the last 4 days. The SUM that is connected to the UTM updates successfully. 
 I restarted the UTM this morning in the hope that might trigger the failing item. I have two other UTMs running 9.402-7 and they are updating correctly. I have re-applied the up2date settings. 
 The licence is current and doesn't expire for another two years. The following is an extract from the up2date log. 
 2016:05:19-18:53:01 cats-kingdom audld[29619]: Starting Up2Date Package Downloader
2016:05:19-18:53:01 cats-kingdom audld[29619]: patch up2date possible
2016:05:19-18:53:39 cats-kingdom audld[29619]: Could not connect to Server 175.41.132.12 (status=500 proxy connect failed: alarm).
2016:05:19-18:54:14 cats-kingdom audld[29619]: Could not connect to Server 107.21.214.248 (status=500 proxy connect failed: alarm).
2016:05:19-18:54:49 cats-kingdom audld[29619]: Could not connect to Server 54.214.16.252 (status=500 proxy connect failed: Any hints and ideas on how to fix this would be appreciated. updated a typing mistake.

IanMorehouse · Answer

fixed. A little while ago I tried an experiment to have the SUM cache the updates and decided that didn't really work in my environment and thinking about the concept it has big holes in it. 
 Download the up2date patterns then send them out on a slow link, means double handling by the UTM and being logged against your useage twice by your ISP. 
 The fix was to remove the SUM cache setting in the UTM. Still leaves a bug where the utm is trying to authenticate to the up2date servers and failing. The error message is not really helpful.