I don't think the UI code is the problematic as much as are the drivers. For example F8 and FR970 have different screens this IMHO brings different drivers and how these interact with the internal GPU. So even though at the UI level they might be similar they still continue to be different. 

As I said thankfully and maybe luckily I have no issue with the FR970 (except of the failed backup restore from F8 - some things were transfered some not), occational screen lag to turn on and sometimes it turns on with minor movement when not intended to be glanced upon. But this is my use case and my use case is pure sport watch. I dont need another 'smart' device to disturb me and bomb me with unnecesary notifications so I purely use the FR as sporting device. I do get notifications when on of course but I almost never leave the BT on :)

I had the 965. Might give the Amazfit Balance 2 a try as the specs seem good. 

the volume issue discussed earlier on F8 in this thread, was seen and fix on F7 recently, it is now present on FRx55/x65 too.

the base of the system is the same since years, but different teams create different branches ... 

The best solution should be a One System for all, with features based on Model ID.

Sorry are you suggesting you 970 is more accurate than the Epix Pro? Because mine most definitely isn't! There is a new supposedly more efficient chip in the Fenix 8 and 970 Which.os nowhere near as good as my Epix Pro. The 970 drifts at virtually every slightly difficult location. Trees, small building including next to standard houses. Comparing GPS tracks side by side you can clearly see this. Also distances are clearly wrong compared to the Epix Pro. 

Yes, my Epix pro was drifting like your FR970, same traces with FR970, city running, buildings, bridges, trees out of city.... The turnings and traces are a lot of clearer than on Epix pro for me.... That accuracy is one thing why I don't want to use Epix pro back.

Very strange my original and replacement 970 are both the same. The Epix is definitely more accurate. Did you use multiband with the Epix?

Yep I used, now I double checked activities from epix on almost same weather and I am right, FR970 are more precise .. especially on turns.... I hope of se update fix problems to you... If some day someone remember that fr970 are needed to update. 

Yeah... If it is not working for you, return them. I am 50/50 of returning them too - i bought them cause phone assistant, calling, message replying etc. Other things was working on Epix - but the reality is that i dont use phone assistant, calling, because 4 of 5 attempts cause triangle of death, then 4 of 5 attempts are working, so unstable function which I dont use because I am afraid of crash. 

For example: Colleague in work asked me: Hey, you have new forerunner watched, cool - show me how the assistant is working, I am thinking about leaving Samsung while garmin have phone assistant too. Me: Ok, no problem. Watches: crash, restart, after restart I was apologizing Garmin thats fresh watch and normal to sometimes crash, tried to show him again, next crash... :D 
So probably I did best marketing which Garmin deserves, he told that he will stick with his samsung ecosystem :-D.

I don't use it either now and if it was the only thing that didn't work I'd probably get over it. But there is just too much wrong.