This is more of an observation than a question, although I would certainly entertain comments and suggestions.
I have numerous ROKUs attached to various TVs and AVRs, all with CEC enabled. The ROKUs all generally work as expected, however, very infrequently my Ultra disappears from the CEC device list on a SONY TV connected through a SONY AVR. Restarting the Ultra brings it back.
During Black Friday sales, I picked up an Amazon Fire 4K Stick, just to try, and connected it to the SONY TV through the SONY AVR. Immediately the ROKU Ultra began to frequently drop from the SONY's CEC list. Removing the Fire 4K Stick returned the Ultra to its usual CEC stability. I moved the Fire 4K Stick to a Samsung TV & Onkyo AVR setup where a ROKU Stick+ has been completely CEC stable. Almost immediately, the ROKU Stick+ began frequently falling off the CEC list in that setup. In every case, the Fire 4K Stick and other CEC devices remained connected--only the ROKU devices fell off the CEC device lists.
Acknowledging that my ROKU Ultra would infrequently drop from the SONY TV's CEC list, I did some experimenting. It seems that the Ultra occasionally drops from the SONY CEC list after turning on and using a SONY 4K UHD player which is also CEC enabled to the SONY TV.
It seems that all/some ROKU devices have CEC compatibility issues with some other CEC devices. My ROKUs seem to have no problem coexisting with Google Chromecast devices, but really don't like being connected alongside an Amazon 4K Stick and/or an infrequently used Sony UHD blu-ray player.
Anyone observe similar behavior in your environment? Any suggestions to improve the situation?