Just to keeping the information up to date…
I’m trying to find the problem in my system with the invaluable help of Steve Harris (@Stevesky ) and at the moment it seems to be some mysterious and inexplicable problem with my Tidal account which, for some mysterious reason, loses the connection with the Naim App, it seems that something is blocking or disrupting that conversation between the App and Tidal hence and the favorites never make it to Tidal.
We’ll continue and see…
Yes - I did do that too - remove standby to never when I first got the ND555 years ago as I did not want it doing that. I think that was the only thing I changes since I had it - until yesterday! 
DB.
No, I think it was someone else who was pointing out that you aren’t really leaving it properly “switched on” 24/7 without having server mode switched to on and that the current being drawn with server mode switched off wasn’t even enough to power a USB socket let alone the Naim itself. I found a worthwhile improvement in a matter of hours of having that setting on. A more full bodied sound. I have to listen mostly on headphones and they were becoming fatiguing after a short period. They no longer do.
I recall being very vocal with the Initial 2.3.6 if I recall correctly, was directed for me and some others, but the majority where fine.
With this recent change it is the other way around, I like it.
However one point remains from both experiences, first time round my major issue was, I demonstrated, I buy based on a sound and take it home.
It seems now for Naim, it appears with other OEMs not such an issue, but then none have a forum to gauge except hifi wigwam.
So one day you loving your system, firmware for a new feature drops, you upgrade and now you have a different sound, this is a difficult pill to swallow.
Last time round Naim offered a downgrade, but then you loose feature updates and more importantly you won’t get any updates.
Tricky one but very worrying for customers and Naim.
I thought server mode keeps the unit on 24/7, so it never really goes into standby.
So no warm up when starts as it has already been cooking
No problem - I did mention it on this thread a day ago if you look, but if there was someone before then I do not want to take credit, especially as I get the opposite result! 
Good to try these thing and decide for yourself, like you have, always best IMO.
I’ve often preferred a different presentation to another - different and right for me but not for them is all.
DB.
There is another setting on the App above that called ‘auto standby time’ you can set to ‘never’ and that does that without the Server needing to be running.
In any case I did that change a day ago and it was still on 24h later.
DB.
I wonder if setting the standby time to ‘never’ is in fact the same as enabling server mode, insofar as both will keep the main transformer warmed up.
My auto standby time has long been set to never but strangely I have never noticed a warm up time affecting the sound before I used that setting. Server Mode seems to have made a noticeable difference for me. It’s beginning to sound like it doesn’t have much to do with ‘warming up’ after all. I wonder why it sounds better for me and not for you. All very strange. The original post about it was several days ago. I hadn’t seen yours from yesterday. I will have a look.
Well they are two different options so I expect you need one for the other but not visa-versa.
Server off should be just disabling that option, whereas standby is putting everything into power-conservation mode.
My Dealer (I think) recommended the standby ‘off’ was what they do as a matter of course as they want to have the item always ready warmed-up for demo.
If I later decide to put it back on and like it - I’ll do it! 
It is a small effect that I found worthwhile when trying it.
DB.
I thought never standby has been in the settings for ages
The issue seems to be that any software changes to control software can affect noise which may have a good or bad effect on the sound entirely independent of any planned tweaks to the sound.
The sound is good, so have no issue with the changes in the sound…
You may be right - I do not recall if I did it or my Dealer, or it was default!
DB.
I bought my Star about 2 years ago and auto standby was not set to ‘never’ by default but I soon changed it after reading about it on here.
Like its predecessor, this new firmware update raises strong reactions regarding changes in sound.
And the fact that the 3.5 release presents some usability issues doesn’t help…
To get to the bottom of it, I spent some time this evening listening to the HiFi (not the music) using some test tracks.
For me, in all audiophile areas, the progression from 3.3 to 3.4 and now the 3.5 is a delight!
Details, airiness, three dimensional soundstage, etc. Everything is so much better. Especially comparing to the 3.3 release.
The following track is, in my opinion, extremely difficult to reproduce and is one of my favourite tests.
With the 3.3 firmware it was so so… a bit blurry and quite flat to be honest!
It is now so much better!
From 3.3 to 3.5 the change is huge, the ND555 is transformed.
The fourth and final movement.
I think your mean stability issues more than usability. Self restarting systems is not a sign of a stable software environment. Since switching back to 3.4 mines back to normal operation wise. No glitches, fast to respond and so far no self restarts.
Right, that’s what I meant.
Let’s hope Naim solves those problems, without introducing others, in the very likely 3.5.1 release.
Playing with options - I’ve tried turning Bluetooth off/on.
Again - initially subtle but after a while it isn’t. Brain seems to take a few minutes or more to utilize the new information there, as I find you are used to what you expect to hear and anything different is at first possibly ‘wrong’ and may not actually be better. To be clear here - Naim have done a good job and it is a ‘small’ change - but I’m now hearing stuff I’ve never heard before with it turned off. I don’t use it - it is easy to put on if I want it - so toggle it off and listening.
First thing is more lucid clarity - less noise grain and a more liquid-sounding presentation. More dynamics and resolution of transients apparent, lower part of female voice better rendered, close notes on synth now clearly separated and their subtle frequency changes between each other there in way I’d not appreciated. And a lot more.
So something else to try if you don’t use it right now.
DB.
… I had my first experience with the NDX 2 go into a stuttering mode while streaming an album from Qobuz. Then the NDX 2 just decided to reboot itself. When it came back on line I played the rest of the album via my NAS since I have a copy ripped from a CD and it played without fail. No time to troubleshoot today with other commitments.
I thought I had dodged a bullet since I had updated several days ago and had not experienced any problems during that time. Strange times indeed and I do hope they get a fix for whatever is causing the problem and release an update for the NDX 2 that has been flawless for the past 18 months.