Take a look at this discussion, quite few ideas on how to resolve Harmony instability. Personally, what worked for me:
My learning from having the same issue - harmony hubs do not like high channel settings, use 1 or 6, avoid 11 - might be unstable (don’t ask me why, found it by trial and error). Same with channel width, limit it to 20MHz, do not use Auto or forced 40MHz. If you have more than 1 AP or mesh network… hubs do not like switching between APs, I had to disable roaming.