Connections 5 runs on WebSphere Application Server 8.5.x.
We recently deployed on the 8.5.5.2 release, but as part of keeping the WAS stack as up to date as possible, I updated to the recent release 8.5.5.3. We were experiencing an error that is resolved in the update.
Details on this fix are located here
Just to save time, if you are going to do the same, uninstall fix IFP119108, or you’ll get the error below when you go to update using IIM.

Hope this saves time for someone out there.
EDIT…It appears that IBM have decided not to support Connections on this version of WAS.
So if you need to update to resolve an issue in the WAS stack, beware…