Sorry to hear about yoru continued problems.
I had the same for months. I got a second HE hub. I moved all risky devices/apps to the old hub. My older HE hub ran faster than my newer hub with all my rules. It didnt fix the problem. I bought a Xbee to trace/map my Zigbee network. It wasnt the problem.
I finally decided to move my automations to NodeRed, and use Hubitat for device control only. I'm not fully there, but 90% of my automations are now with NodeRed.
I experience faster rule running, very few DB errors, and better satisfaction. My experience has led me to believe that HE struggles with many rules. My backup size has reduced from 35MB to 19 MB.
My recomendation: look into Node Red. I also have a pretty cool dashboard too.
