Okay cool - but keep in mind I have no idea how your system is set up, what kinds of devices, how they are paired (S0,S2,None), the layout what other issues might be impacting etc etc. It could be a firmware update or maybe a faulty device.. or a bunch of other stuff. Something that is obvious to you in your environment might not be to me.. 
My understanding is the newer firmware tries to be more active in looking for better routes so maybe thats part of it. You can restore to a previous version via the diagnostic tools.
To kind of answer your troubleshooting question - you start with the logs, looks at the app/device stats, look at the Z-Wave details / Check out the Zigbee child reports etc. Submit a ticket to support as well if things are not progressing.
A bunch of us in this community also have UZB-7 sticks (or older Z-Sticks and others) which we pair to the HE as a secondary controller - it allows us to do things like remove ghosts, update firmware if unable to in HE, view certain details not accessible from HE. Very useful.
Another thing that can be done is Zniffing - monitoring the Z-Wave traffic to see whats going on.
