Yes, it is.
The strange thing is that the original datafield (DatarunppremiumApp) builds fine with the midrange watches. The midrange watches have a different resourcepath, in the sourcepath are some files shared with the high end watches. The background process is for the Tempe; that is new for the update, and the storage function is also new.
The copy version has one variable more and memory and objects are tight. It might be that the compiler is behaving strangely because of that?
So, finally found it. I had created a 2nd baseApp file, for the midrange watches with the last update of the main version. My monkey file pointed towards the directory it was in, but I completely forgot about it and didn't also change "class DatarunpremiumApp extends Toybox.Application.AppBase {" in "class Datarunpremiumwith7metricscopy2App extends Toybox.Application.AppBase {" there.
Jim was right, as he always is. Now if only the compiler could give the hints that Jim does...