New XB8 randomly dropping devices

Just recently swapped my XB7 for the new XB8 modem.  Was hopping for better device connectivity and expanded coverage. I have a very old home and complicated construction so network coverage can be difficult. I currently have over 40 devices connected to my network (smart switches, Echos, TVs, security cameras...) I was running fine on the XB7 for a couple of years until we had summer parties and then connectivity would be spotty. I was hoping the new XB8 would solve this problem but it has created a new one in the past couple of weeks.  I am now getting random devices dropping from my network. Sometimes my phone, sometimes my laptop but these can be easily corrected on the device however  a bit annoying and no where near what I had on my XB7.  My biggest issue is with my music receiver which runs three outdoor music zones.  The only way to reconnect this device to the network is to unplug the unit and and reconnect which at best only lasts a couple of hours.  The receiver is connected to the XB8 box via CAT5 (tried different wires). After a soft boot the receiver will connect to the network fine and work perfectly. I can see the device and its IP address in the Xfinity app but after an hour or so it disappears of the device list. I have been trying a bunch of stuff on my receiver end to try and get it to stay connected... I reset the receiver to factory settings, upgraded the firmware, set the network standby to ON so it should stay connected. I have also played with DHCP to fake the receiver to think it has a dedicated IP (I realize Xfinity does not support this on residential installs) hoping the receiver/modem will not try to refresh the IP.  NOTHING has worked on the receiver end and it was working fine on the XB7 modem before I upgraded.  Because I am still getting random phone and laptop drops (once or twice daily) I am leaning towards something going on with the XB8 dropping device connectivity.... ANY HELP would be greatly appreciated!!!! TIA