iOS App is unstable, or is it?

[Will]

This is an issue that has emerged in the firmware 12.3.0 thread and has been mentioned in a few other topics recently.  I thought I would start a new thread to see if we can solve this one because I now know it has little to do with firmware versions.

Last night I tried a little experiment.  I collected together four IOS devices, loaded the Devialet app onto those devices that did not already have it, reloaded the app onto those devices that did have it, to make sure the app versions are identical.  All devices were connected to the same wifi network and controlling the same Devialet amp.  The only variable here is the IOS device itself.  The results were interesting, as follows:

iPhone 5 - app 100% stable for over one hour
iPhone 6 Plus - app unstable, dropping out and reconnecting every few minutes
iPad AIR 2 - app unstable, dropping out and reconnecting every few minutes
iPhone 7 - app 100% stable for over one hour

Unfortunately, I do not have a latest iPhone 8 or X to try, but I am intrigued that in the above mini test it was the oldest and the newest device that proved stable (the iPhone 5 and 7), the "middle-aged" devices were very unstable. (iPhone 6 Plus and iPad AIR 2).

So I am guessing it is some kind of incompatibility issue with certain iOS devices, or maybe a particular setting in IOS.  For the record, the unstable iPhone 6 Plus and the stable iPhone 7 were running identical / latest versions of iOS.  (iOS 11.4)

So it is nothing to do with the Devialet, network or wifi, this was a constant for the four devices tried here.  It has to be an incompatibility with some aspect of the iOS device itself.

Any ideas?

I have an iPad Air 2 and have never had problems with the Devialet App - which suggests that the problem with the Devialet App may be at the individual device level.  A few months ago, I was noticing all sorts of problems with my iPad (but not with the Devialet App). A complete factory reset, and reloading only those apps I was actually using has made a big difference in performance.